Use failure instead of error_chain. (#586) r=nalexander

Cargo.toml

@@ -28,7 +28,8 @@ rustc_version = "0.2"
 
 [dependencies]
 chrono = "0.4"
-error-chain = { git = "https://github.com/rnewman/error-chain", branch = "rnewman/sync" }
+failure = "0.1.1"
+failure_derive = "0.1.1"
 lazy_static = "0.2"
 time = "0.1"
 uuid = { version = "0.5", features = ["v4", "serde"] }

core/Cargo.toml

@@ -6,6 +6,7 @@ workspace = ".."
 [dependencies]
 chrono = { version = "0.4", features = ["serde"] }
 enum-set = { git = "https://github.com/rnewman/enum-set" }
+failure = "0.1.1"
 indexmap = "1"
 lazy_static = "0.2"
 num = "0.1"

core/src/cache.rs

@@ -10,6 +10,8 @@
 
 /// Cache traits.
 
+use failure;
+
 use std::collections::{
     BTreeSet,
 };
@@ -33,8 +35,7 @@ pub trait CachedAttributes {
     fn get_entids_for_value(&self, attribute: Entid, value: &TypedValue) -> Option<&BTreeSet<Entid>>;
 }
 
-pub trait UpdateableCache {
-    type Error;
-    fn update<I>(&mut self, schema: &Schema, retractions: I, assertions: I) -> Result<(), Self::Error>
+pub trait UpdateableCache<Error=failure::Error> {
+    fn update<I>(&mut self, schema: &Schema, retractions: I, assertions: I) -> Result<(), Error>
     where I: Iterator<Item=(Entid, Entid, TypedValue)>;
 }

core/src/lib.rs

@@ -10,6 +10,7 @@
 
 extern crate chrono;
 extern crate enum_set;
+extern crate failure;
 extern crate indexmap;
 extern crate ordered_float;
 extern crate uuid;

db/Cargo.toml

@@ -8,7 +8,8 @@ default = []
 sqlcipher = ["rusqlite/sqlcipher"]
 
 [dependencies]
-error-chain = { git = "https://github.com/rnewman/error-chain", branch = "rnewman/sync" }
+failure = "0.1.1"
+failure_derive = "0.1.1"
 indexmap = "1"
 itertools = "0.7"
 lazy_static = "0.2"

db/src/bootstrap.rs

@@ -11,7 +11,10 @@
 #![allow(dead_code)]
 
 use edn;
-use errors::{ErrorKind, Result};
+use errors::{
+    DbError,
+    Result,
+};
 use edn::types::Value;
 use edn::symbols;
 use entids;
@@ -156,7 +159,7 @@ lazy_static! {
                         :db/cardinality :db.cardinality/many}}"#;
         edn::parse::value(s)
             .map(|v| v.without_spans())
-            .map_err(|_| ErrorKind::BadBootstrapDefinition("Unable to parse V1_SYMBOLIC_SCHEMA".into()))
+            .map_err(|_| DbError::BadBootstrapDefinition("Unable to parse V1_SYMBOLIC_SCHEMA".into()))
             .unwrap()
     };
 }
@@ -207,14 +210,14 @@ fn symbolic_schema_to_triples(ident_map: &IdentMap, symbolic_schema: &Value) ->
             for (ident, mp) in m {
                 let ident = match ident {
                     &Value::Keyword(ref ident) => ident,
-                    _ => bail!(ErrorKind::BadBootstrapDefinition(format!("Expected namespaced keyword for ident but got '{:?}'", ident))),
+                    _ => bail!(DbError::BadBootstrapDefinition(format!("Expected namespaced keyword for ident but got '{:?}'", ident))),
                 };
                 match *mp {
                     Value::Map(ref mpp) => {
                         for (attr, value) in mpp {
                             let attr = match attr {
                                 &Value::Keyword(ref attr) => attr,
-                                _ => bail!(ErrorKind::BadBootstrapDefinition(format!("Expected namespaced keyword for attr but got '{:?}'", attr))),
+                                _ => bail!(DbError::BadBootstrapDefinition(format!("Expected namespaced keyword for attr but got '{:?}'", attr))),
                         };
 
                             // We have symbolic idents but the transactor handles entids.  Ad-hoc
@@ -229,20 +232,20 @@ fn symbolic_schema_to_triples(ident_map: &IdentMap, symbolic_schema: &Value) ->
                                 Some(TypedValue::Keyword(ref k)) => {
                                     ident_map.get(k)
                                         .map(|entid| TypedValue::Ref(*entid))
-                                        .ok_or(ErrorKind::UnrecognizedIdent(k.to_string()))?
+                                        .ok_or(DbError::UnrecognizedIdent(k.to_string()))?
                                 },
                                 Some(v) => v,
-                                _ => bail!(ErrorKind::BadBootstrapDefinition(format!("Expected Mentat typed value for value but got '{:?}'", value)))
+                                _ => bail!(DbError::BadBootstrapDefinition(format!("Expected Mentat typed value for value but got '{:?}'", value)))
                             };
 
                             triples.push((ident.clone(), attr.clone(), typed_value));
                         }
                     },
-                    _ => bail!(ErrorKind::BadBootstrapDefinition("Expected {:db/ident {:db/attr value ...} ...}".into()))
+                    _ => bail!(DbError::BadBootstrapDefinition("Expected {:db/ident {:db/attr value ...} ...}".into()))
                 }
             }
         },
-        _ => bail!(ErrorKind::BadBootstrapDefinition("Expected {...}".into()))
+        _ => bail!(DbError::BadBootstrapDefinition("Expected {...}".into()))
     }
     Ok(triples)
 }
@@ -263,11 +266,11 @@ fn symbolic_schema_to_assertions(symbolic_schema: &Value) -> Result<Vec<Value>>
                                                                value.clone()]));
                         }
                     },
-                    _ => bail!(ErrorKind::BadBootstrapDefinition("Expected {:db/ident {:db/attr value ...} ...}".into()))
+                    _ => bail!(DbError::BadBootstrapDefinition("Expected {:db/ident {:db/attr value ...} ...}".into()))
                 }
             }
         },
-        _ => bail!(ErrorKind::BadBootstrapDefinition("Expected {...}".into()))
+        _ => bail!(DbError::BadBootstrapDefinition("Expected {...}".into()))
     }
     Ok(assertions)
 }

db/src/cache.rs

@@ -106,7 +106,7 @@ use db::{
 };
 
 use errors::{
-    ErrorKind,
+    DbError,
     Result,
 };
 
@@ -1155,15 +1155,14 @@ impl CachedAttributes for AttributeCaches {
 }
 
 impl UpdateableCache for AttributeCaches {
-    type Error = ::errors::Error;
-    fn update<I>(&mut self, schema: &Schema, retractions: I, assertions: I) -> ::std::result::Result<(), Self::Error>
+    fn update<I>(&mut self, schema: &Schema, retractions: I, assertions: I) -> Result<()>
     where I: Iterator<Item=(Entid, Entid, TypedValue)> {
         self.update_with_fallback(None, schema, retractions, assertions)
     }
 }
 
 impl AttributeCaches {
-    fn update_with_fallback<I>(&mut self, fallback: Option<&AttributeCaches>, schema: &Schema, retractions: I, assertions: I) -> ::std::result::Result<(), ::errors::Error>
+    fn update_with_fallback<I>(&mut self, fallback: Option<&AttributeCaches>, schema: &Schema, retractions: I, assertions: I) -> Result<()>
     where I: Iterator<Item=(Entid, Entid, TypedValue)> {
         let r_aevs = retractions.peekable();
         self.accumulate_into_cache(fallback, schema, r_aevs, AccumulationBehavior::Remove)?;
@@ -1237,7 +1236,7 @@ impl SQLiteAttributeCache {
         let a = attribute.into();
 
         // The attribute must exist!
-        let _ = schema.attribute_for_entid(a).ok_or_else(|| ErrorKind::UnknownAttribute(a))?;
+        let _ = schema.attribute_for_entid(a).ok_or_else(|| DbError::UnknownAttribute(a))?;
         let caches = self.make_mut();
         caches.forward_cached_attributes.insert(a);
         caches.repopulate(schema, sqlite, a)
@@ -1248,7 +1247,7 @@ impl SQLiteAttributeCache {
         let a = attribute.into();
 
         // The attribute must exist!
-        let _ = schema.attribute_for_entid(a).ok_or_else(|| ErrorKind::UnknownAttribute(a))?;
+        let _ = schema.attribute_for_entid(a).ok_or_else(|| DbError::UnknownAttribute(a))?;
 
         let caches = self.make_mut();
         caches.reverse_cached_attributes.insert(a);
@@ -1278,8 +1277,7 @@ impl SQLiteAttributeCache {
 }
 
 impl UpdateableCache for SQLiteAttributeCache {
-    type Error = ::errors::Error;
-    fn update<I>(&mut self, schema: &Schema, retractions: I, assertions: I) -> ::std::result::Result<(), Self::Error>
+    fn update<I>(&mut self, schema: &Schema, retractions: I, assertions: I) -> Result<()>
     where I: Iterator<Item=(Entid, Entid, TypedValue)> {
         self.make_mut().update(schema, retractions, assertions)
     }
@@ -1356,7 +1354,7 @@ impl InProgressSQLiteAttributeCache {
         let a = attribute.into();
 
         // The attribute must exist!
-        let _ = schema.attribute_for_entid(a).ok_or_else(|| ErrorKind::UnknownAttribute(a))?;
+        let _ = schema.attribute_for_entid(a).ok_or_else(|| DbError::UnknownAttribute(a))?;
 
         if self.is_attribute_cached_forward(a) {
             return Ok(());
@@ -1372,7 +1370,7 @@ impl InProgressSQLiteAttributeCache {
         let a = attribute.into();
 
         // The attribute must exist!
-        let _ = schema.attribute_for_entid(a).ok_or_else(|| ErrorKind::UnknownAttribute(a))?;
+        let _ = schema.attribute_for_entid(a).ok_or_else(|| DbError::UnknownAttribute(a))?;
 
         if self.is_attribute_cached_reverse(a) {
             return Ok(());
@@ -1388,7 +1386,7 @@ impl InProgressSQLiteAttributeCache {
         let a = attribute.into();
 
         // The attribute must exist!
-        let _ = schema.attribute_for_entid(a).ok_or_else(|| ErrorKind::UnknownAttribute(a))?;
+        let _ = schema.attribute_for_entid(a).ok_or_else(|| DbError::UnknownAttribute(a))?;
 
         // TODO: reverse-index unique by default?
         let reverse_done = self.is_attribute_cached_reverse(a);
@@ -1427,8 +1425,7 @@ impl InProgressSQLiteAttributeCache {
 }
 
 impl UpdateableCache for InProgressSQLiteAttributeCache {
-    type Error = ::errors::Error;
-    fn update<I>(&mut self, schema: &Schema, retractions: I, assertions: I) -> ::std::result::Result<(), Self::Error>
+    fn update<I>(&mut self, schema: &Schema, retractions: I, assertions: I) -> Result<()>
     where I: Iterator<Item=(Entid, Entid, TypedValue)> {
         self.overlay.update_with_fallback(Some(&self.inner), schema, retractions, assertions)
     }

db/src/db.rs

@@ -10,6 +10,8 @@
 
 #![allow(dead_code)]
 
+use failure::ResultExt;
+
 use std::borrow::Borrow;
 use std::collections::HashMap;
 use std::collections::hash_map::{
@@ -53,7 +55,11 @@ use mentat_core::{
     ValueRc,
 };
 
-use errors::{ErrorKind, Result, ResultExt};
+use errors::{
+    DbError,
+    Result,
+    DbSqlErrorKind,
+};
 use metadata;
 use schema::{
     SchemaBuilding,
@@ -251,8 +257,8 @@ lazy_static! {
 /// documentation](https://www.sqlite.org/pragma.html#pragma_user_version).
 fn set_user_version(conn: &rusqlite::Connection, version: i32) -> Result<()> {
     conn.execute(&format!("PRAGMA user_version = {}", version), &[])
-        .chain_err(|| "Could not set_user_version")
-        .map(|_| ())
+        .context(DbSqlErrorKind::CouldNotSetVersionPragma)?;
+    Ok(())
 }
 
 /// Get the SQLite user version.
@@ -260,10 +266,10 @@ fn set_user_version(conn: &rusqlite::Connection, version: i32) -> Result<()> {
 /// Mentat manages its own SQL schema version using the user version.  See the [SQLite
 /// documentation](https://www.sqlite.org/pragma.html#pragma_user_version).
 fn get_user_version(conn: &rusqlite::Connection) -> Result<i32> {
-    conn.query_row("PRAGMA user_version", &[], |row| {
+    let v = conn.query_row("PRAGMA user_version", &[], |row| {
         row.get(0)
-    })
-        .chain_err(|| "Could not get_user_version")
+    }).context(DbSqlErrorKind::CouldNotGetVersionPragma)?;
+    Ok(v)
 }
 
 /// Do just enough work that either `create_current_version` or sync can populate the DB.
@@ -303,8 +309,7 @@ pub fn create_current_version(conn: &mut rusqlite::Connection) -> Result<DB> {
     // TODO: validate metadata mutations that aren't schema related, like additional partitions.
     if let Some(next_schema) = next_schema {
         if next_schema != db.schema {
-            // TODO Use custom ErrorKind https://github.com/brson/error-chain/issues/117
-            bail!(ErrorKind::NotYetImplemented(format!("Initial bootstrap transaction did not produce expected bootstrap schema")));
+            bail!(DbError::NotYetImplemented(format!("Initial bootstrap transaction did not produce expected bootstrap schema")));
         }
     }
 
@@ -326,7 +331,7 @@ pub fn ensure_current_version(conn: &mut rusqlite::Connection) -> Result<DB> {
         CURRENT_VERSION => read_db(conn),
 
         // TODO: support updating an existing store.
-        v => bail!(ErrorKind::NotYetImplemented(format!("Opening databases with Mentat version: {}", v))),
+        v => bail!(DbError::NotYetImplemented(format!("Opening databases with Mentat version: {}", v))),
     }
 }
 
@@ -356,7 +361,7 @@ impl TypedSQLValue for TypedValue {
                 let u = Uuid::from_bytes(x.as_slice());
                 if u.is_err() {
                     // Rather than exposing Uuid's ParseError…
-                    bail!(ErrorKind::BadSQLValuePair(rusqlite::types::Value::Blob(x),
+                    bail!(DbError::BadSQLValuePair(rusqlite::types::Value::Blob(x),
                                                      value_type_tag));
                 }
                 Ok(TypedValue::Uuid(u.unwrap()))
@@ -364,7 +369,7 @@ impl TypedSQLValue for TypedValue {
             (13, rusqlite::types::Value::Text(x)) => {
                 to_namespaced_keyword(&x).map(|k| k.into())
             },
-            (_, value) => bail!(ErrorKind::BadSQLValuePair(value, value_type_tag)),
+            (_, value) => bail!(DbError::BadSQLValuePair(value, value_type_tag)),
         }
     }
 
@@ -447,12 +452,12 @@ fn read_ident_map(conn: &rusqlite::Connection) -> Result<IdentMap> {
     let v = read_materialized_view(conn, "idents")?;
     v.into_iter().map(|(e, a, typed_value)| {
         if a != entids::DB_IDENT {
-            bail!(ErrorKind::NotYetImplemented(format!("bad idents materialized view: expected :db/ident but got {}", a)));
+            bail!(DbError::NotYetImplemented(format!("bad idents materialized view: expected :db/ident but got {}", a)));
         }
         if let TypedValue::Keyword(keyword) = typed_value {
             Ok((keyword.as_ref().clone(), e))
         } else {
-            bail!(ErrorKind::NotYetImplemented(format!("bad idents materialized view: expected [entid :db/ident keyword] but got [entid :db/ident {:?}]", typed_value)));
+            bail!(DbError::NotYetImplemented(format!("bad idents materialized view: expected [entid :db/ident keyword] but got [entid :db/ident {:?}]", typed_value)));
         }
     }).collect()
 }
@@ -546,9 +551,8 @@ fn search(conn: &rusqlite::Connection) -> Result<()> {
          t.a0 = d.a"#;
 
     let mut stmt = conn.prepare_cached(s)?;
-    stmt.execute(&[])
-        .map(|_c| ())
-        .chain_err(|| "Could not search!")
+    stmt.execute(&[]).context(DbSqlErrorKind::CouldNotSearch)?;
+    Ok(())
 }
 
 /// Insert the new transaction into the `transactions` table.
@@ -570,9 +574,7 @@ fn insert_transaction(conn: &rusqlite::Connection, tx: Entid) -> Result<()> {
       WHERE added0 IS 1 AND ((rid IS NULL) OR ((rid IS NOT NULL) AND (v0 IS NOT v)))"#;
 
     let mut stmt = conn.prepare_cached(s)?;
-    stmt.execute(&[&tx])
-        .map(|_c| ())
-        .chain_err(|| "Could not insert transaction: failed to add datoms not already present")?;
+    stmt.execute(&[&tx]).context(DbSqlErrorKind::TxInsertFailedToAddMissingDatoms)?;
 
     let s = r#"
       INSERT INTO transactions (e, a, v, tx, added, value_type_tag)
@@ -583,9 +585,7 @@ fn insert_transaction(conn: &rusqlite::Connection, tx: Entid) -> Result<()> {
              (added0 IS 1 AND search_type IS ':db.cardinality/one' AND v0 IS NOT v))"#;
 
     let mut stmt = conn.prepare_cached(s)?;
-    stmt.execute(&[&tx])
-        .map(|_c| ())
-        .chain_err(|| "Could not insert transaction: failed to retract datoms already present")?;
+    stmt.execute(&[&tx]).context(DbSqlErrorKind::TxInsertFailedToRetractDatoms)?;
 
     Ok(())
 }
@@ -607,9 +607,7 @@ fn update_datoms(conn: &rusqlite::Connection, tx: Entid) -> Result<()> {
         DELETE FROM datoms WHERE rowid IN ids"#;
 
     let mut stmt = conn.prepare_cached(s)?;
-    stmt.execute(&[])
-        .map(|_c| ())
-        .chain_err(|| "Could not update datoms: failed to retract datoms already present")?;
+    stmt.execute(&[]).context(DbSqlErrorKind::DatomsUpdateFailedToRetract)?;
 
     // Insert datoms that were added and not already present. We also must expand our bitfield into
     // flags.  Since Mentat follows Datomic and treats its input as a set, it is okay to transact
@@ -632,10 +630,7 @@ fn update_datoms(conn: &rusqlite::Connection, tx: Entid) -> Result<()> {
       AttributeBitFlags::UniqueValue as u8);
 
     let mut stmt = conn.prepare_cached(&s)?;
-    stmt.execute(&[&tx])
-        .map(|_c| ())
-        .chain_err(|| "Could not update datoms: failed to add datoms not already present")?;
-
+    stmt.execute(&[&tx]).context(DbSqlErrorKind::DatomsUpdateFailedToAdd)?;
     Ok(())
 }
 
@@ -762,9 +757,7 @@ impl MentatStoring for rusqlite::Connection {
 
         for statement in &statements {
             let mut stmt = self.prepare_cached(statement)?;
-            stmt.execute(&[])
-                .map(|_c| ())
-                .chain_err(|| "Failed to create temporary tables")?;
+            stmt.execute(&[]).context(DbSqlErrorKind::FailedToCreateTempTables)?;
         }
 
         Ok(())
@@ -827,8 +820,9 @@ impl MentatStoring for rusqlite::Connection {
             // TODO: consider ensuring we inserted the expected number of rows.
             let mut stmt = self.prepare_cached(s.as_str())?;
             stmt.execute(&params)
+                .context(DbSqlErrorKind::NonFtsInsertionIntoTempSearchTableFailed)
+                .map_err(|e| e.into())
                 .map(|_c| ())
-                .chain_err(|| "Could not insert non-fts one statements into temporary search table!")
         }).collect::<Result<Vec<()>>>();
 
         results.map(|_| ())
@@ -886,7 +880,7 @@ impl MentatStoring for rusqlite::Connection {
                         }
                     },
                     _ => {
-                        bail!("Cannot transact a fulltext assertion with a typed value that is not :db/valueType :db.type/string");
+                        bail!(DbError::WrongTypeValueForFtsAssertion);
                     },
                 }
 
@@ -913,9 +907,7 @@ impl MentatStoring for rusqlite::Connection {
 
             // TODO: consider ensuring we inserted the expected number of rows.
             let mut stmt = self.prepare_cached(fts_s.as_str())?;
-            stmt.execute(&fts_params)
-                .map(|_c| ())
-                .chain_err(|| "Could not insert fts values into fts table!")?;
+            stmt.execute(&fts_params).context(DbSqlErrorKind::FtsInsertionFailed)?;
 
             // Second, insert searches.
             // `params` reference computed values in `block`.
@@ -943,17 +935,14 @@ impl MentatStoring for rusqlite::Connection {
 
             // TODO: consider ensuring we inserted the expected number of rows.
             let mut stmt = self.prepare_cached(s.as_str())?;
-            stmt.execute(&params)
+            stmt.execute(&params).context(DbSqlErrorKind::FtsInsertionIntoTempSearchTableFailed)
+                .map_err(|e| e.into())
                 .map(|_c| ())
-                .chain_err(|| "Could not insert FTS statements into temporary search table!")
         }).collect::<Result<Vec<()>>>();
 
         // Finally, clean up temporary searchids.
         let mut stmt = self.prepare_cached("UPDATE fulltext_values SET searchid = NULL WHERE searchid IS NOT NULL")?;
-        stmt.execute(&[])
-            .map(|_c| ())
-            .chain_err(|| "Could not drop FTS search ids!")?;
-
+        stmt.execute(&[]).context(DbSqlErrorKind::FtsFailedToDropSearchIds)?;
         results.map(|_| ())
     }
 
@@ -985,7 +974,7 @@ pub fn update_partition_map(conn: &rusqlite::Connection, partition_map: &Partiti
     let max_vars = conn.limit(Limit::SQLITE_LIMIT_VARIABLE_NUMBER) as usize;
     let max_partitions = max_vars / values_per_statement;
     if partition_map.len() > max_partitions {
-        bail!(ErrorKind::NotYetImplemented(format!("No more than {} partitions are supported", max_partitions)));
+        bail!(DbError::NotYetImplemented(format!("No more than {} partitions are supported", max_partitions)));
     }
 
     // Like "UPDATE parts SET idx = CASE WHEN part = ? THEN ? WHEN part = ? THEN ? ELSE idx END".
@@ -1001,9 +990,8 @@ pub fn update_partition_map(conn: &rusqlite::Connection, partition_map: &Partiti
     // supported in the Clojure implementation at all, and might not be supported in Mentat soon,
     // so this is very low priority.
     let mut stmt = conn.prepare_cached(s.as_str())?;
-    stmt.execute(&params[..])
-        .map(|_c| ())
-        .chain_err(|| "Could not update partition map")
+    stmt.execute(&params[..]).context(DbSqlErrorKind::FailedToUpdatePartitionMap)?;
+    Ok(())
 }
 
 /// Update the metadata materialized views based on the given metadata report.
@@ -1062,8 +1050,8 @@ SELECT EXISTS
                     // error message in this case.
                     if unique_value_stmt.execute(&[to_bool_ref(attribute.unique.is_some()), &entid as &ToSql]).is_err() {
                         match attribute.unique {
-                            Some(attribute::Unique::Value) => bail!(ErrorKind::SchemaAlterationFailed(format!("Cannot alter schema attribute {} to be :db.unique/value", entid))),
-                            Some(attribute::Unique::Identity) => bail!(ErrorKind::SchemaAlterationFailed(format!("Cannot alter schema attribute {} to be :db.unique/identity", entid))),
+                            Some(attribute::Unique::Value) => bail!(DbError::SchemaAlterationFailed(format!("Cannot alter schema attribute {} to be :db.unique/value", entid))),
+                            Some(attribute::Unique::Identity) => bail!(DbError::SchemaAlterationFailed(format!("Cannot alter schema attribute {} to be :db.unique/identity", entid))),
                             None => unreachable!(), // This shouldn't happen, even after we support removing :db/unique.
                         }
                     }
@@ -1077,7 +1065,7 @@ SELECT EXISTS
                     if !attribute.multival {
                         let mut rows = cardinality_stmt.query(&[&entid as &ToSql])?;
                         if rows.next().is_some() {
-                            bail!(ErrorKind::SchemaAlterationFailed(format!("Cannot alter schema attribute {} to be :db.cardinality/one", entid)));
+                            bail!(DbError::SchemaAlterationFailed(format!("Cannot alter schema attribute {} to be :db.cardinality/one", entid)));
                         }
                     }
                 },
@@ -2684,8 +2672,8 @@ mod tests {
 
         let report = conn.transact_simple_terms(terms, InternSet::new());
 
-        match report.unwrap_err() {
-            errors::Error(ErrorKind::SchemaConstraintViolation(errors::SchemaConstraintViolation::TypeDisagreements { conflicting_datoms }), _) => {
+        match report.unwrap_err().downcast() {
+            Ok(DbError::SchemaConstraintViolation(errors::SchemaConstraintViolation::TypeDisagreements { conflicting_datoms })) => {
                 let mut map = BTreeMap::default();
                 map.insert((100, entids::DB_TX_INSTANT, TypedValue::Long(-1)), ValueType::Instant);
                 map.insert((200, entids::DB_IDENT, TypedValue::typed_string("test")), ValueType::Keyword);

db/src/errors.rs

@@ -10,6 +10,13 @@
 
 #![allow(dead_code)]
 
+use failure::{
+    Backtrace,
+    Context,
+    Error,
+    Fail,
+};
+
 use std::collections::{
     BTreeMap,
     BTreeSet,
@@ -29,6 +36,16 @@ use types::{
     ValueType,
 };
 
+#[macro_export]
+macro_rules! bail {
+    ($e:expr) => (
+        return Err($e.into());
+    )
+}
+
+pub type Result<T> = ::std::result::Result<T, Error>;
+
+// TODO Error/ErrorKind pair
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub enum CardinalityConflict {
     /// A cardinality one attribute has multiple assertions `[e a v1], [e a v2], ...`.
@@ -46,7 +63,8 @@ pub enum CardinalityConflict {
     },
 }
 
-#[derive(Clone, Debug, Eq, PartialEq)]
+// TODO Error/ErrorKind pair
+#[derive(Clone, Debug, Eq, PartialEq, Fail)]
 pub enum SchemaConstraintViolation {
     /// A transaction tried to assert datoms where one tempid upserts to two (or more) distinct
     /// entids.
@@ -125,95 +143,145 @@ impl ::std::fmt::Display for InputError {
     }
 }
 
-error_chain! {
-    types {
-        Error, ErrorKind, ResultExt, Result;
-    }
-
-    foreign_links {
-        Rusqlite(rusqlite::Error);
-    }
-
-    errors {
+#[derive(Debug, Fail)]
+pub enum DbError {
     /// We're just not done yet.  Message that the feature is recognized but not yet
     /// implemented.
-        NotYetImplemented(t: String) {
-            description("not yet implemented")
-            display("not yet implemented: {}", t)
-        }
+    #[fail(display = "not yet implemented: {}", _0)]
+    NotYetImplemented(String),
 
     /// We've been given a value that isn't the correct Mentat type.
-        BadValuePair(value: String, value_type: ValueType) {
-            description("value is not the expected Mentat value type")
-            display("value '{}' is not the expected Mentat value type {:?}", value, value_type)
-        }
+    #[fail(display = "value '{}' is not the expected Mentat value type {:?}", _0, _1)]
+    BadValuePair(String, ValueType),
 
     /// We've got corrupt data in the SQL store: a value and value_type_tag don't line up.
-        BadSQLValuePair(value: rusqlite::types::Value, value_type_tag: i32) {
-            description("bad SQL (value_type_tag, value) pair")
-            display("bad SQL (value_type_tag, value) pair: ({}, {:?})", value_type_tag, value.data_type())
-        }
+    /// TODO _1.data_type()
+    #[fail(display = "bad SQL (value_type_tag, value) pair: ({:?}, {:?})", _0, _1)]
+    BadSQLValuePair(rusqlite::types::Value, i32),
 
     // /// The SQLite store user_version isn't recognized.  This could be an old version of Mentat
     // /// trying to open a newer version SQLite store; or it could be a corrupt file; or ...
-        // BadSQLiteStoreVersion(version: i32) {
-        //     description("bad SQL store user_version")
-        //     display("bad SQL store user_version: {}", version)
-        // }
+    // #[fail(display = "bad SQL store user_version: {}", _0)]
+    // BadSQLiteStoreVersion(i32),
 
     /// A bootstrap definition couldn't be parsed or installed.  This is a programmer error, not
     /// a runtime error.
-        BadBootstrapDefinition(t: String) {
-            description("bad bootstrap definition")
-            display("bad bootstrap definition: {}", t)
-        }
+    #[fail(display = "bad bootstrap definition: {}", _0)]
+    BadBootstrapDefinition(String),
 
     /// A schema assertion couldn't be parsed.
-        BadSchemaAssertion(t: String) {
-            description("bad schema assertion")
-            display("bad schema assertion: {}", t)
-        }
+    #[fail(display = "bad schema assertion: {}", _0)]
+    BadSchemaAssertion(String),
 
     /// An ident->entid mapping failed.
-        UnrecognizedIdent(ident: String) {
-            description("no entid found for ident")
-            display("no entid found for ident: {}", ident)
-        }
+    #[fail(display = "no entid found for ident: {}", _0)]
+    UnrecognizedIdent(String),
 
     /// An entid->ident mapping failed.
     /// We also use this error if you try to transact an entid that we didn't allocate,
     /// in part because we blow the stack in error_chain if we define a new enum!
-        UnrecognizedEntid(entid: Entid) {
-            description("unrecognized or no ident found for entid")
-            display("unrecognized or no ident found for entid: {}", entid)
-        }
+    #[fail(display = "unrecognized or no ident found for entid: {}", _0)]
+    UnrecognizedEntid(Entid),
 
-        UnknownAttribute(attr: Entid) {
-            description("unknown attribute")
-            display("unknown attribute for entid: {}", attr)
-        }
+    #[fail(display = "unknown attribute for entid: {}", _0)]
+    UnknownAttribute(Entid),
 
-        CannotCacheNonUniqueAttributeInReverse(attr: Entid) {
-            description("cannot reverse-cache non-unique attribute")
-            display("cannot reverse-cache non-unique attribute: {}", attr)
-        }
+    #[fail(display = "cannot reverse-cache non-unique attribute: {}", _0)]
+    CannotCacheNonUniqueAttributeInReverse(Entid),
 
-        SchemaAlterationFailed(t: String) {
-            description("schema alteration failed")
-            display("schema alteration failed: {}", t)
-        }
+    #[fail(display = "schema alteration failed: {}", _0)]
+    SchemaAlterationFailed(String),
 
     /// A transaction tried to violate a constraint of the schema of the Mentat store.
-        SchemaConstraintViolation(violation: SchemaConstraintViolation) {
-            description("schema constraint violation")
-            display("schema constraint violation: {}", violation)
-        }
+    #[fail(display = "schema constraint violation: {}", _0)]
+    SchemaConstraintViolation(SchemaConstraintViolation),
 
     /// The transaction was malformed in some way (that was not recognized at parse time; for
     /// example, in a way that is schema-dependent).
-        InputError(error: InputError) {
-            description("transaction input error")
-            display("transaction input error: {}", error)
+    #[fail(display = "transaction input error: {}", _0)]
+    InputError(InputError),
+
+    #[fail(display = "Cannot transact a fulltext assertion with a typed value that is not :db/valueType :db.type/string")]
+    WrongTypeValueForFtsAssertion,
+}
+
+#[derive(Debug)]
+pub struct DbSqlError {
+    inner: Context<DbSqlErrorKind>,
+}
+
+impl Fail for DbSqlError {
+    fn cause(&self) -> Option<&Fail> {
+        self.inner.cause()
     }
+
+    fn backtrace(&self) -> Option<&Backtrace> {
+        self.inner.backtrace()
     }
 }
+
+impl ::std::fmt::Display for DbSqlError {
+    fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        ::std::fmt::Display::fmt(&self.inner, f)
+    }
+}
+
+impl DbSqlError {
+    pub fn kind(&self) -> DbSqlErrorKind {
+        *self.inner.get_context()
+    }
+}
+
+impl From<DbSqlErrorKind> for DbSqlError {
+    fn from(kind: DbSqlErrorKind) -> DbSqlError {
+        DbSqlError { inner: Context::new(kind) }
+    }
+}
+
+impl From<Context<DbSqlErrorKind>> for DbSqlError {
+    fn from(inner: Context<DbSqlErrorKind>) -> DbSqlError {
+        DbSqlError { inner: inner }
+    }
+}
+
+#[derive(Copy, Clone, Eq, PartialEq, Debug, Fail)]
+pub enum DbSqlErrorKind {
+    #[fail(display = "Could not set_user_version")]
+    CouldNotSetVersionPragma,
+
+    #[fail(display = "Could not get_user_version")]
+    CouldNotGetVersionPragma,
+
+    #[fail(display = "Could not search!")]
+    CouldNotSearch,
+
+    #[fail(display = "Could not insert transaction: failed to add datoms not already present")]
+    TxInsertFailedToAddMissingDatoms,
+
+    #[fail(display = "Could not insert transaction: failed to retract datoms already present")]
+    TxInsertFailedToRetractDatoms,
+
+    #[fail(display = "Could not update datoms: failed to retract datoms already present")]
+    DatomsUpdateFailedToRetract,
+
+    #[fail(display = "Could not update datoms: failed to add datoms not already present")]
+    DatomsUpdateFailedToAdd,
+
+    #[fail(display = "Failed to create temporary tables")]
+    FailedToCreateTempTables,
+
+    #[fail(display = "Could not insert non-fts one statements into temporary search table!")]
+    NonFtsInsertionIntoTempSearchTableFailed,
+
+    #[fail(display = "Could not insert fts values into fts table!")]
+    FtsInsertionFailed,
+
+    #[fail(display = "Could not insert FTS statements into temporary search table!")]
+    FtsInsertionIntoTempSearchTableFailed,
+
+    #[fail(display = "Could not drop FTS search ids!")]
+    FtsFailedToDropSearchIds,
+
+    #[fail(display = "Could not update partition map")]
+    FailedToUpdatePartitionMap,
+}

db/src/internal_types.rs

@@ -31,7 +31,7 @@ use edn::{
 
 use errors;
 use errors::{
-    ErrorKind,
+    DbError,
     Result,
 };
 use schema::{
@@ -69,7 +69,7 @@ impl TransactableValue for ValueAndSpan {
                     Ok(EntityPlace::Entid(entities::Entid::Ident(v)))
                 } else {
                     // We only allow namespaced idents.
-                    bail!(ErrorKind::InputError(errors::InputError::BadEntityPlace))
+                    bail!(DbError::InputError(errors::InputError::BadEntityPlace))
                 }
             },
             Text(v) => Ok(EntityPlace::TempId(TempId::External(v))),
@@ -86,10 +86,10 @@ impl TransactableValue for ValueAndSpan {
                             EntityPlace::Entid(a) => Ok(EntityPlace::LookupRef(entities::LookupRef { a: entities::AttributePlace::Entid(a), v: v.clone() })),
                             EntityPlace::TempId(_) |
                             EntityPlace::TxFunction(_) |
-                            EntityPlace::LookupRef(_) => bail!(ErrorKind::InputError(errors::InputError::BadEntityPlace)),
+                            EntityPlace::LookupRef(_) => bail!(DbError::InputError(errors::InputError::BadEntityPlace)),
                         }
                     },
-                    _ => bail!(ErrorKind::InputError(errors::InputError::BadEntityPlace)),
+                    _ => bail!(DbError::InputError(errors::InputError::BadEntityPlace)),
                 }
             },
             Nil |
@@ -102,7 +102,7 @@ impl TransactableValue for ValueAndSpan {
             NamespacedSymbol(_) |
             Vector(_) |
             Set(_) |
-            Map(_) => bail!(ErrorKind::InputError(errors::InputError::BadEntityPlace)),
+            Map(_) => bail!(DbError::InputError(errors::InputError::BadEntityPlace)),
         }
     }
 
@@ -114,7 +114,7 @@ impl TransactableValue for ValueAndSpan {
 impl TransactableValue for TypedValue {
     fn into_typed_value(self, _schema: &Schema, value_type: ValueType) -> Result<TypedValue> {
         if self.value_type() != value_type {
-            bail!(ErrorKind::BadValuePair(format!("{:?}", self), value_type));
+            bail!(DbError::BadValuePair(format!("{:?}", self), value_type));
         }
         Ok(self)
     }
@@ -128,7 +128,7 @@ impl TransactableValue for TypedValue {
             TypedValue::Long(_) |
             TypedValue::Double(_) |
             TypedValue::Instant(_) |
-            TypedValue::Uuid(_) => bail!(ErrorKind::InputError(errors::InputError::BadEntityPlace)),
+            TypedValue::Uuid(_) => bail!(DbError::InputError(errors::InputError::BadEntityPlace)),
         }
     }
 
@@ -199,7 +199,7 @@ pub fn replace_lookup_ref<T, U>(lookup_map: &AVMap, desired_or: Either<T, Lookup
                 LookupRefOrTempId::LookupRef(av) => lookup_map.get(&*av)
                     .map(|x| lift(*x)).map(Left)
                     // XXX TODO: fix this error kind!
-                    .ok_or_else(|| ErrorKind::UnrecognizedIdent(format!("couldn't lookup [a v]: {:?}", (*av).clone())).into()),
+                    .ok_or_else(|| DbError::UnrecognizedIdent(format!("couldn't lookup [a v]: {:?}", (*av).clone())).into()),
             }
         }
     }

db/src/lib.rs

@@ -8,10 +8,8 @@
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
 
-// Oh, error_chain.
-#![recursion_limit="128"]
-
-#[macro_use] extern crate error_chain;
+extern crate failure;
+#[macro_use] extern crate failure_derive;
 extern crate indexmap;
 extern crate itertools;
 #[macro_use] extern crate lazy_static;
@@ -31,7 +29,12 @@ use std::iter::repeat;
 
 use itertools::Itertools;
 
-pub use errors::{Error, ErrorKind, ResultExt, Result};
+pub use errors::{
+    DbError,
+    Result,
+    SchemaConstraintViolation,
+};
+#[macro_use] pub mod errors;
 
 mod add_retract_alter_set;
 pub mod cache;
@@ -39,7 +42,6 @@ pub mod db;
 mod bootstrap;
 pub mod debug;
 pub mod entids;
-pub mod errors;
 pub mod internal_types;    // pub because we need them for building entities programmatically.
 mod metadata;
 mod schema;
@@ -114,8 +116,7 @@ pub fn to_namespaced_keyword(s: &str) -> Result<symbols::Keyword> {
         _ => None,
     };
 
-    // TODO Use custom ErrorKind https://github.com/brson/error-chain/issues/117
-    nsk.ok_or(ErrorKind::NotYetImplemented(format!("InvalidKeyword: {}", s)).into())
+    nsk.ok_or(DbError::NotYetImplemented(format!("InvalidKeyword: {}", s)).into())
 }
 
 /// Prepare an SQL `VALUES` block, like (?, ?, ?), (?, ?, ?).

db/src/metadata.rs

@@ -24,6 +24,8 @@
 //!
 //! This module recognizes, validates, applies, and reports on these mutations.
 
+use failure::ResultExt;
+
 use std::collections::{BTreeMap, BTreeSet};
 use std::collections::btree_map::Entry;
 
@@ -33,9 +35,8 @@ use add_retract_alter_set::{
 use edn::symbols;
 use entids;
 use errors::{
-    ErrorKind,
+    DbError,
     Result,
-    ResultExt,
 };
 use mentat_core::{
     attribute,
@@ -131,7 +132,7 @@ pub fn update_attribute_map_from_entid_triples<A, R>(attribute_map: &mut Attribu
                         builder.component(false);
                     },
                     v => {
-                        bail!(ErrorKind::BadSchemaAssertion(format!("Attempted to retract :db/isComponent with the wrong value {:?}.", v)));
+                        bail!(DbError::BadSchemaAssertion(format!("Attempted to retract :db/isComponent with the wrong value {:?}.", v)));
                     },
                 }
             },
@@ -146,15 +147,15 @@ pub fn update_attribute_map_from_entid_triples<A, R>(attribute_map: &mut Attribu
                                 builder.non_unique();
                             },
                             v => {
-                                bail!(ErrorKind::BadSchemaAssertion(format!("Attempted to retract :db/unique with the wrong value {}.", v)));
+                                bail!(DbError::BadSchemaAssertion(format!("Attempted to retract :db/unique with the wrong value {}.", v)));
                             },
                         }
                     },
-                    _ => bail!(ErrorKind::BadSchemaAssertion(format!("Expected [:db/retract _ :db/unique :db.unique/_] but got [:db/retract {} :db/unique {:?}]", entid, value)))
+                    _ => bail!(DbError::BadSchemaAssertion(format!("Expected [:db/retract _ :db/unique :db.unique/_] but got [:db/retract {} :db/unique {:?}]", entid, value)))
                 }
             },
             _ => {
-                bail!(ErrorKind::BadSchemaAssertion(format!("Retracting attribute {} for entity {} not permitted.", attr, entid)));
+                bail!(DbError::BadSchemaAssertion(format!("Retracting attribute {} for entity {} not permitted.", attr, entid)));
             },
         }
     }
@@ -168,7 +169,7 @@ pub fn update_attribute_map_from_entid_triples<A, R>(attribute_map: &mut Attribu
             entids::DB_DOC => {
                 match *value {
                     TypedValue::String(_) => {},
-                    _ => bail!(ErrorKind::BadSchemaAssertion(format!("Expected [... :db/doc \"string value\"] but got [... :db/doc {:?}] for entid {} and attribute {}", value, entid, attr)))
+                    _ => bail!(DbError::BadSchemaAssertion(format!("Expected [... :db/doc \"string value\"] but got [... :db/doc {:?}] for entid {} and attribute {}", value, entid, attr)))
                 }
             },
 
@@ -182,7 +183,7 @@ pub fn update_attribute_map_from_entid_triples<A, R>(attribute_map: &mut Attribu
                     TypedValue::Ref(entids::DB_TYPE_REF)     => { builder.value_type(ValueType::Ref); },
                     TypedValue::Ref(entids::DB_TYPE_STRING)  => { builder.value_type(ValueType::String); },
                     TypedValue::Ref(entids::DB_TYPE_UUID)    => { builder.value_type(ValueType::Uuid); },
-                    _ => bail!(ErrorKind::BadSchemaAssertion(format!("Expected [... :db/valueType :db.type/*] but got [... :db/valueType {:?}] for entid {} and attribute {}", value, entid, attr)))
+                    _ => bail!(DbError::BadSchemaAssertion(format!("Expected [... :db/valueType :db.type/*] but got [... :db/valueType {:?}] for entid {} and attribute {}", value, entid, attr)))
                 }
             },
 
@@ -190,7 +191,7 @@ pub fn update_attribute_map_from_entid_triples<A, R>(attribute_map: &mut Attribu
                 match *value {
                     TypedValue::Ref(entids::DB_CARDINALITY_MANY) => { builder.multival(true); },
                     TypedValue::Ref(entids::DB_CARDINALITY_ONE) => { builder.multival(false); },
-                    _ => bail!(ErrorKind::BadSchemaAssertion(format!("Expected [... :db/cardinality :db.cardinality/many|:db.cardinality/one] but got [... :db/cardinality {:?}]", value)))
+                    _ => bail!(DbError::BadSchemaAssertion(format!("Expected [... :db/cardinality :db.cardinality/many|:db.cardinality/one] but got [... :db/cardinality {:?}]", value)))
                 }
             },
 
@@ -198,40 +199,40 @@ pub fn update_attribute_map_from_entid_triples<A, R>(attribute_map: &mut Attribu
                 match *value {
                     TypedValue::Ref(entids::DB_UNIQUE_VALUE) => { builder.unique(attribute::Unique::Value); },
                     TypedValue::Ref(entids::DB_UNIQUE_IDENTITY) => { builder.unique(attribute::Unique::Identity); },
-                    _ => bail!(ErrorKind::BadSchemaAssertion(format!("Expected [... :db/unique :db.unique/value|:db.unique/identity] but got [... :db/unique {:?}]", value)))
+                    _ => bail!(DbError::BadSchemaAssertion(format!("Expected [... :db/unique :db.unique/value|:db.unique/identity] but got [... :db/unique {:?}]", value)))
                 }
             },
 
             entids::DB_INDEX => {
                 match *value {
                     TypedValue::Boolean(x) => { builder.index(x); },
-                    _ => bail!(ErrorKind::BadSchemaAssertion(format!("Expected [... :db/index true|false] but got [... :db/index {:?}]", value)))
+                    _ => bail!(DbError::BadSchemaAssertion(format!("Expected [... :db/index true|false] but got [... :db/index {:?}]", value)))
                 }
             },
 
             entids::DB_FULLTEXT => {
                 match *value {
                     TypedValue::Boolean(x) => { builder.fulltext(x); },
-                    _ => bail!(ErrorKind::BadSchemaAssertion(format!("Expected [... :db/fulltext true|false] but got [... :db/fulltext {:?}]", value)))
+                    _ => bail!(DbError::BadSchemaAssertion(format!("Expected [... :db/fulltext true|false] but got [... :db/fulltext {:?}]", value)))
                 }
             },
 
             entids::DB_IS_COMPONENT => {
                 match *value {
                     TypedValue::Boolean(x) => { builder.component(x); },
-                    _ => bail!(ErrorKind::BadSchemaAssertion(format!("Expected [... :db/isComponent true|false] but got [... :db/isComponent {:?}]", value)))
+                    _ => bail!(DbError::BadSchemaAssertion(format!("Expected [... :db/isComponent true|false] but got [... :db/isComponent {:?}]", value)))
                 }
             },
 
             entids::DB_NO_HISTORY => {
                 match *value {
                     TypedValue::Boolean(x) => { builder.no_history(x); },
-                    _ => bail!(ErrorKind::BadSchemaAssertion(format!("Expected [... :db/noHistory true|false] but got [... :db/noHistory {:?}]", value)))
+                    _ => bail!(DbError::BadSchemaAssertion(format!("Expected [... :db/noHistory true|false] but got [... :db/noHistory {:?}]", value)))
                 }
             },
 
             _ => {
-                bail!(ErrorKind::BadSchemaAssertion(format!("Do not recognize attribute {} for entid {}", attr, entid)))
+                bail!(DbError::BadSchemaAssertion(format!("Do not recognize attribute {} for entid {}", attr, entid)))
             }
         }
     };
@@ -243,8 +244,7 @@ pub fn update_attribute_map_from_entid_triples<A, R>(attribute_map: &mut Attribu
         match attribute_map.entry(entid) {
             Entry::Vacant(entry) => {
                 // Validate once…
-                builder.validate_install_attribute()
-                       .chain_err(|| ErrorKind::BadSchemaAssertion(format!("Schema alteration for new attribute with entid {} is not valid", entid)))?;
+                builder.validate_install_attribute().context(DbError::BadSchemaAssertion(format!("Schema alteration for new attribute with entid {} is not valid", entid)))?;
 
                 // … and twice, now we have the Attribute.
                 let a = builder.build();
@@ -254,8 +254,7 @@ pub fn update_attribute_map_from_entid_triples<A, R>(attribute_map: &mut Attribu
             },
 
             Entry::Occupied(mut entry) => {
-                builder.validate_alter_attribute()
-                       .chain_err(|| ErrorKind::BadSchemaAssertion(format!("Schema alteration for existing attribute with entid {} is not valid", entid)))?;
+                builder.validate_alter_attribute().context(DbError::BadSchemaAssertion(format!("Schema alteration for existing attribute with entid {} is not valid", entid)))?;
                 let mutations = builder.mutate(entry.get_mut());
                 attributes_altered.insert(entid, mutations);
             },

db/src/schema.rs

@@ -12,7 +12,10 @@
 
 use db::TypedSQLValue;
 use edn;
-use errors::{ErrorKind, Result};
+use errors::{
+    DbError,
+    Result,
+};
 use edn::symbols;
 use mentat_core::{
     attribute,
@@ -39,19 +42,19 @@ pub trait AttributeValidation {
 impl AttributeValidation for Attribute {
     fn validate<F>(&self, ident: F) -> Result<()> where F: Fn() -> String {
         if self.unique == Some(attribute::Unique::Value) && !self.index {
-            bail!(ErrorKind::BadSchemaAssertion(format!(":db/unique :db/unique_value without :db/index true for entid: {}", ident())))
+            bail!(DbError::BadSchemaAssertion(format!(":db/unique :db/unique_value without :db/index true for entid: {}", ident())))
         }
         if self.unique == Some(attribute::Unique::Identity) && !self.index {
-            bail!(ErrorKind::BadSchemaAssertion(format!(":db/unique :db/unique_identity without :db/index true for entid: {}", ident())))
+            bail!(DbError::BadSchemaAssertion(format!(":db/unique :db/unique_identity without :db/index true for entid: {}", ident())))
         }
         if self.fulltext && self.value_type != ValueType::String {
-            bail!(ErrorKind::BadSchemaAssertion(format!(":db/fulltext true without :db/valueType :db.type/string for entid: {}", ident())))
+            bail!(DbError::BadSchemaAssertion(format!(":db/fulltext true without :db/valueType :db.type/string for entid: {}", ident())))
         }
         if self.fulltext && !self.index {
-            bail!(ErrorKind::BadSchemaAssertion(format!(":db/fulltext true without :db/index true for entid: {}", ident())))
+            bail!(DbError::BadSchemaAssertion(format!(":db/fulltext true without :db/index true for entid: {}", ident())))
         }
         if self.component && self.value_type != ValueType::Ref {
-            bail!(ErrorKind::BadSchemaAssertion(format!(":db/isComponent true without :db/valueType :db.type/ref for entid: {}", ident())))
+            bail!(DbError::BadSchemaAssertion(format!(":db/isComponent true without :db/valueType :db.type/ref for entid: {}", ident())))
         }
         // TODO: consider warning if we have :db/index true for :db/valueType :db.type/string,
         // since this may be inefficient.  More generally, we should try to drive complex
@@ -150,17 +153,17 @@ impl AttributeBuilder {
 
     pub fn validate_install_attribute(&self) -> Result<()> {
         if self.value_type.is_none() {
-            bail!(ErrorKind::BadSchemaAssertion("Schema attribute for new attribute does not set :db/valueType".into()));
+            bail!(DbError::BadSchemaAssertion("Schema attribute for new attribute does not set :db/valueType".into()));
         }
         Ok(())
     }
 
     pub fn validate_alter_attribute(&self) -> Result<()> {
         if self.value_type.is_some() {
-            bail!(ErrorKind::BadSchemaAssertion("Schema alteration must not set :db/valueType".into()));
+            bail!(DbError::BadSchemaAssertion("Schema alteration must not set :db/valueType".into()));
         }
         if self.fulltext.is_some() {
-            bail!(ErrorKind::BadSchemaAssertion("Schema alteration must not set :db/fulltext".into()));
+            bail!(DbError::BadSchemaAssertion("Schema alteration must not set :db/fulltext".into()));
         }
         Ok(())
     }
@@ -247,15 +250,15 @@ pub trait SchemaBuilding {
 
 impl SchemaBuilding for Schema {
     fn require_ident(&self, entid: Entid) -> Result<&symbols::Keyword> {
-        self.get_ident(entid).ok_or(ErrorKind::UnrecognizedEntid(entid).into())
+        self.get_ident(entid).ok_or(DbError::UnrecognizedEntid(entid).into())
     }
 
     fn require_entid(&self, ident: &symbols::Keyword) -> Result<KnownEntid> {
-        self.get_entid(&ident).ok_or(ErrorKind::UnrecognizedIdent(ident.to_string()).into())
+        self.get_entid(&ident).ok_or(DbError::UnrecognizedIdent(ident.to_string()).into())
     }
 
     fn require_attribute_for_entid(&self, entid: Entid) -> Result<&Attribute> {
-        self.attribute_for_entid(entid).ok_or(ErrorKind::UnrecognizedEntid(entid).into())
+        self.attribute_for_entid(entid).ok_or(DbError::UnrecognizedEntid(entid).into())
     }
 
     /// Create a valid `Schema` from the constituent maps.
@@ -271,8 +274,8 @@ impl SchemaBuilding for Schema {
         where U: IntoIterator<Item=(symbols::Keyword, symbols::Keyword, TypedValue)>{
 
         let entid_assertions: Result<Vec<(Entid, Entid, TypedValue)>> = assertions.into_iter().map(|(symbolic_ident, symbolic_attr, value)| {
-            let ident: i64 = *ident_map.get(&symbolic_ident).ok_or(ErrorKind::UnrecognizedIdent(symbolic_ident.to_string()))?;
-            let attr: i64 = *ident_map.get(&symbolic_attr).ok_or(ErrorKind::UnrecognizedIdent(symbolic_attr.to_string()))?;
+            let ident: i64 = *ident_map.get(&symbolic_ident).ok_or(DbError::UnrecognizedIdent(symbolic_ident.to_string()))?;
+            let attr: i64 = *ident_map.get(&symbolic_attr).ok_or(DbError::UnrecognizedIdent(symbolic_attr.to_string()))?;
             Ok((ident, attr, value))
         }).collect();
 
@@ -305,7 +308,7 @@ impl SchemaTypeChecking for Schema {
         // wrapper function.
         match TypedValue::from_edn_value(&value.clone().without_spans()) {
             // We don't recognize this EDN at all.  Get out!
-            None => bail!(ErrorKind::BadValuePair(format!("{}", value), value_type)),
+            None => bail!(DbError::BadValuePair(format!("{}", value), value_type)),
             Some(typed_value) => match (value_type, typed_value) {
                 // Most types don't coerce at all.
                 (ValueType::Boolean, tv @ TypedValue::Boolean(_)) => Ok(tv),
@@ -331,7 +334,7 @@ impl SchemaTypeChecking for Schema {
                 (vt @ ValueType::Instant, _) |
                 (vt @ ValueType::Keyword, _) |
                 (vt @ ValueType::Ref, _)
-                => bail!(ErrorKind::BadValuePair(format!("{}", value), vt)),
+                => bail!(DbError::BadValuePair(format!("{}", value), vt)),
             }
         }
     }
@@ -343,7 +346,6 @@ impl SchemaTypeChecking for Schema {
 mod test {
     use super::*;
     use self::edn::Keyword;
-    use errors::Error;
 
     fn add_attribute(schema: &mut Schema,
             ident: Keyword,
@@ -435,8 +437,8 @@ mod test {
         let err = validate_attribute_map(&schema.entid_map, &schema.attribute_map).err();
         assert!(err.is_some());
 
-        match err.unwrap() {
-            Error(ErrorKind::BadSchemaAssertion(message), _) => { assert_eq!(message, ":db/unique :db/unique_value without :db/index true for entid: :foo/bar"); },
+        match err.unwrap().downcast() {
+            Ok(DbError::BadSchemaAssertion(message)) => { assert_eq!(message, ":db/unique :db/unique_value without :db/index true for entid: :foo/bar"); },
             x => panic!("expected Bad Schema Assertion error, got {:?}", x),
         }
     }
@@ -458,8 +460,8 @@ mod test {
         let err = validate_attribute_map(&schema.entid_map, &schema.attribute_map).err();
         assert!(err.is_some());
 
-        match err.unwrap() {
-            Error(ErrorKind::BadSchemaAssertion(message), _) => { assert_eq!(message, ":db/unique :db/unique_identity without :db/index true for entid: :foo/bar"); },
+        match err.unwrap().downcast() {
+            Ok(DbError::BadSchemaAssertion(message)) => { assert_eq!(message, ":db/unique :db/unique_identity without :db/index true for entid: :foo/bar"); },
             x => panic!("expected Bad Schema Assertion error, got {:?}", x),
         }
     }
@@ -481,8 +483,8 @@ mod test {
         let err = validate_attribute_map(&schema.entid_map, &schema.attribute_map).err();
         assert!(err.is_some());
 
-        match err.unwrap() {
-            Error(ErrorKind::BadSchemaAssertion(message), _) => { assert_eq!(message, ":db/isComponent true without :db/valueType :db.type/ref for entid: :foo/bar"); },
+        match err.unwrap().downcast() {
+            Ok(DbError::BadSchemaAssertion(message)) => { assert_eq!(message, ":db/isComponent true without :db/valueType :db.type/ref for entid: :foo/bar"); },
             x => panic!("expected Bad Schema Assertion error, got {:?}", x),
         }
     }
@@ -504,8 +506,8 @@ mod test {
         let err = validate_attribute_map(&schema.entid_map, &schema.attribute_map).err();
         assert!(err.is_some());
 
-        match err.unwrap() {
-            Error(ErrorKind::BadSchemaAssertion(message), _) => { assert_eq!(message, ":db/fulltext true without :db/index true for entid: :foo/bar"); },
+        match err.unwrap().downcast() {
+            Ok(DbError::BadSchemaAssertion(message)) => { assert_eq!(message, ":db/fulltext true without :db/index true for entid: :foo/bar"); },
             x => panic!("expected Bad Schema Assertion error, got {:?}", x),
         }
     }
@@ -526,8 +528,8 @@ mod test {
         let err = validate_attribute_map(&schema.entid_map, &schema.attribute_map).err();
         assert!(err.is_some());
 
-        match err.unwrap() {
-            Error(ErrorKind::BadSchemaAssertion(message), _) => { assert_eq!(message, ":db/fulltext true without :db/valueType :db.type/string for entid: :foo/bar"); },
+        match err.unwrap().downcast() {
+            Ok(DbError::BadSchemaAssertion(message)) => { assert_eq!(message, ":db/fulltext true without :db/valueType :db.type/string for entid: :foo/bar"); },
             x => panic!("expected Bad Schema Assertion error, got {:?}", x),
         }
     }

db/src/tx.rs

@@ -71,7 +71,7 @@ use edn::{
 use entids;
 use errors;
 use errors::{
-    ErrorKind,
+    DbError,
     Result,
 };
 use internal_types::{
@@ -179,7 +179,7 @@ pub fn remove_db_id<V: TransactableValue>(map: &mut entmod::MapNotation<V>) -> R
             entmod::ValuePlace::Atom(v) => Some(v.into_entity_place()?),
             entmod::ValuePlace::Vector(_) |
             entmod::ValuePlace::MapNotation(_) => {
-                bail!(ErrorKind::InputError(errors::InputError::BadDbId))
+                bail!(DbError::InputError(errors::InputError::BadDbId))
             },
         }
     } else {
@@ -244,7 +244,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
         }
 
         if !conflicting_upserts.is_empty() {
-            bail!(ErrorKind::SchemaConstraintViolation(errors::SchemaConstraintViolation::ConflictingUpserts { conflicting_upserts }));
+            bail!(DbError::SchemaConstraintViolation(errors::SchemaConstraintViolation::ConflictingUpserts { conflicting_upserts }));
         }
 
         Ok(tempids)
@@ -281,7 +281,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
                 if self.partition_map.contains_entid(e) {
                     Ok(KnownEntid(e))
                 } else {
-                    bail!(ErrorKind::UnrecognizedEntid(e))
+                    bail!(DbError::UnrecognizedEntid(e))
                 }
             }
 
@@ -298,7 +298,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
 
                 let lr_typed_value: TypedValue = lookup_ref.v.clone().into_typed_value(&self.schema, lr_attribute.value_type)?;
                 if lr_attribute.unique.is_none() {
-                    bail!(ErrorKind::NotYetImplemented(format!("Cannot resolve (lookup-ref {} {:?}) with attribute that is not :db/unique", lr_a, lr_typed_value)))
+                    bail!(DbError::NotYetImplemented(format!("Cannot resolve (lookup-ref {} {:?}) with attribute that is not :db/unique", lr_a, lr_typed_value)))
                 }
 
                 Ok(self.lookup_refs.intern((lr_a, lr_typed_value)))
@@ -336,7 +336,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
                     entmod::EntityPlace::TxFunction(ref tx_function) => {
                         match tx_function.op.0.as_str() {
                             "transaction-tx" => Ok(Either::Left(self.tx_id)),
-                            unknown @ _ => bail!(ErrorKind::NotYetImplemented(format!("Unknown transaction function {}", unknown))),
+                            unknown @ _ => bail!(DbError::NotYetImplemented(format!("Unknown transaction function {}", unknown))),
                         }
                     },
                 }
@@ -357,13 +357,13 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
             fn entity_v_into_term_e<W: TransactableValue>(&mut self, x: entmod::ValuePlace<W>, backward_a: &entmod::Entid) -> Result<KnownEntidOr<LookupRefOrTempId>> {
                 match backward_a.unreversed() {
                     None => {
-                        bail!(ErrorKind::NotYetImplemented(format!("Cannot explode map notation value in :attr/_reversed notation for forward attribute")));
+                        bail!(DbError::NotYetImplemented(format!("Cannot explode map notation value in :attr/_reversed notation for forward attribute")));
                     },
                     Some(forward_a) => {
                         let forward_a = self.entity_a_into_term_a(forward_a)?;
                         let forward_attribute = self.schema.require_attribute_for_entid(forward_a)?;
                         if forward_attribute.value_type != ValueType::Ref {
-                            bail!(ErrorKind::NotYetImplemented(format!("Cannot use :attr/_reversed notation for attribute {} that is not :db/valueType :db.type/ref", forward_a)))
+                            bail!(DbError::NotYetImplemented(format!("Cannot use :attr/_reversed notation for attribute {} that is not :db/valueType :db.type/ref", forward_a)))
                         }
 
                         match x {
@@ -378,7 +378,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
                                             Ok(Either::Left(KnownEntid(entid)))
                                         } else {
                                             // The given value is expected to be :db.type/ref, so this shouldn't happen.
-                                            bail!(ErrorKind::NotYetImplemented(format!("Cannot use :attr/_reversed notation for attribute {} with value that is not :db.valueType :db.type/ref", forward_a)))
+                                            bail!(DbError::NotYetImplemented(format!("Cannot use :attr/_reversed notation for attribute {} with value that is not :db.valueType :db.type/ref", forward_a)))
                                         }
                                     }
                                 }
@@ -396,15 +396,15 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
                             entmod::ValuePlace::TxFunction(ref tx_function) => {
                                 match tx_function.op.0.as_str() {
                                     "transaction-tx" => Ok(Either::Left(KnownEntid(self.tx_id.0))),
-                                    unknown @ _ => bail!(ErrorKind::NotYetImplemented(format!("Unknown transaction function {}", unknown))),
+                                    unknown @ _ => bail!(DbError::NotYetImplemented(format!("Unknown transaction function {}", unknown))),
                                 }
                             },
 
                             entmod::ValuePlace::Vector(_) =>
-                                bail!(ErrorKind::NotYetImplemented(format!("Cannot explode vector value in :attr/_reversed notation for attribute {}", forward_a))),
+                                bail!(DbError::NotYetImplemented(format!("Cannot explode vector value in :attr/_reversed notation for attribute {}", forward_a))),
 
                             entmod::ValuePlace::MapNotation(_) =>
-                                bail!(ErrorKind::NotYetImplemented(format!("Cannot explode map notation value in :attr/_reversed notation for attribute {}", forward_a))),
+                                bail!(DbError::NotYetImplemented(format!("Cannot explode map notation value in :attr/_reversed notation for attribute {}", forward_a))),
                         }
                     },
                 }
@@ -475,7 +475,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
 
                             entmod::ValuePlace::LookupRef(ref lookup_ref) => {
                                 if attribute.value_type != ValueType::Ref {
-                                    bail!(ErrorKind::NotYetImplemented(format!("Cannot resolve value lookup ref for attribute {} that is not :db/valueType :db.type/ref", a)))
+                                    bail!(DbError::NotYetImplemented(format!("Cannot resolve value lookup ref for attribute {} that is not :db/valueType :db.type/ref", a)))
                                 }
 
                                 Either::Right(LookupRefOrTempId::LookupRef(in_process.intern_lookup_ref(lookup_ref)?))
@@ -484,7 +484,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
                             entmod::ValuePlace::TxFunction(ref tx_function) => {
                                 let typed_value = match tx_function.op.0.as_str() {
                                     "transaction-tx" => TypedValue::Ref(self.tx_id),
-                                    unknown @ _ => bail!(ErrorKind::NotYetImplemented(format!("Unknown transaction function {}", unknown))),
+                                    unknown @ _ => bail!(DbError::NotYetImplemented(format!("Unknown transaction function {}", unknown))),
                                 };
 
                                 // Here we do schema-aware typechecking: we assert that the computed
@@ -494,7 +494,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
                                 // value can be used where a double is expected.  See also
                                 // `SchemaTypeChecking.to_typed_value(...)`.
                                 if attribute.value_type != typed_value.value_type() {
-                                    bail!(ErrorKind::NotYetImplemented(format!("Transaction function {} produced value of type {} but expected type {}",
+                                    bail!(DbError::NotYetImplemented(format!("Transaction function {} produced value of type {} but expected type {}",
                                                                                tx_function.op.0.as_str(), typed_value.value_type(), attribute.value_type)));
                                 }
 
@@ -503,7 +503,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
 
                             entmod::ValuePlace::Vector(vs) => {
                                 if !attribute.multival {
-                                    bail!(ErrorKind::NotYetImplemented(format!("Cannot explode vector value for attribute {} that is not :db.cardinality :db.cardinality/many", a)));
+                                    bail!(DbError::NotYetImplemented(format!("Cannot explode vector value for attribute {} that is not :db.cardinality :db.cardinality/many", a)));
                                 }
 
                                 for vv in vs {
@@ -523,11 +523,11 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
                                 // AddOrRetract, which proliferates types and code, or only handling
                                 // nested maps rather than map values, like Datomic does.
                                 if op != OpType::Add {
-                                    bail!(ErrorKind::NotYetImplemented(format!("Cannot explode nested map value in :db/retract for attribute {}", a)));
+                                    bail!(DbError::NotYetImplemented(format!("Cannot explode nested map value in :db/retract for attribute {}", a)));
                                 }
 
                                 if attribute.value_type != ValueType::Ref {
-                                    bail!(ErrorKind::NotYetImplemented(format!("Cannot explode nested map value for attribute {} that is not :db/valueType :db.type/ref", a)))
+                                    bail!(DbError::NotYetImplemented(format!("Cannot explode nested map value for attribute {} that is not :db/valueType :db.type/ref", a)))
                                 }
 
                                 // :db/id is optional; if it's not given, we generate a special internal tempid
@@ -580,7 +580,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
                                 }
 
                                 if dangling {
-                                    bail!(ErrorKind::NotYetImplemented(format!("Cannot explode nested map value that would lead to dangling entity for attribute {}", a)));
+                                    bail!(DbError::NotYetImplemented(format!("Cannot explode nested map value that would lead to dangling entity for attribute {}", a)));
                                 }
 
                                 in_process.entity_e_into_term_v(db_id)?
@@ -668,7 +668,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
             }
 
             if !conflicting_upserts.is_empty() {
-                bail!(ErrorKind::SchemaConstraintViolation(errors::SchemaConstraintViolation::ConflictingUpserts { conflicting_upserts }));
+                bail!(DbError::SchemaConstraintViolation(errors::SchemaConstraintViolation::ConflictingUpserts { conflicting_upserts }));
             }
 
             debug!("tempids {:?}", tempids);
@@ -742,12 +742,12 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
 
         let errors = tx_checking::type_disagreements(&aev_trie);
         if !errors.is_empty() {
-            bail!(ErrorKind::SchemaConstraintViolation(errors::SchemaConstraintViolation::TypeDisagreements { conflicting_datoms: errors }));
+            bail!(DbError::SchemaConstraintViolation(errors::SchemaConstraintViolation::TypeDisagreements { conflicting_datoms: errors }));
         }
 
         let errors = tx_checking::cardinality_conflicts(&aev_trie);
         if !errors.is_empty() {
-            bail!(ErrorKind::SchemaConstraintViolation(errors::SchemaConstraintViolation::CardinalityConflicts { conflicts: errors }));
+            bail!(DbError::SchemaConstraintViolation(errors::SchemaConstraintViolation::CardinalityConflicts { conflicts: errors }));
         }
 
         // Pipeline stage 4: final terms (after rewriting) -> DB insertions.

db/src/upsert_resolution.rs

@@ -21,8 +21,10 @@ use std::collections::{
 use indexmap;
 use petgraph::unionfind;
 
-use errors;
-use errors::ErrorKind;
+use errors::{
+    DbError,
+    Result,
+};
 use types::{
     AVPair,
 };
@@ -100,11 +102,11 @@ pub(crate) struct FinalPopulations {
 impl Generation {
     /// Split entities into a generation of populations that need to evolve to have their tempids
     /// resolved or allocated, and a population of inert entities that do not reference tempids.
-    pub(crate) fn from<I>(terms: I, schema: &Schema) -> errors::Result<(Generation, Population)> where I: IntoIterator<Item=TermWithTempIds> {
+    pub(crate) fn from<I>(terms: I, schema: &Schema) -> Result<(Generation, Population)> where I: IntoIterator<Item=TermWithTempIds> {
         let mut generation = Generation::default();
         let mut inert = vec![];
 
-        let is_unique = |a: Entid| -> errors::Result<bool> {
+        let is_unique = |a: Entid| -> Result<bool> {
             let attribute: &Attribute = schema.require_attribute_for_entid(a)?;
             Ok(attribute.unique == Some(attribute::Unique::Identity))
         };
@@ -223,7 +225,7 @@ impl Generation {
     }
 
     /// Evolve potential upserts that haven't resolved into allocations.
-    pub(crate) fn allocate_unresolved_upserts(&mut self) -> errors::Result<()> {
+    pub(crate) fn allocate_unresolved_upserts(&mut self) -> Result<()> {
         let mut upserts_ev = vec![];
         ::std::mem::swap(&mut self.upserts_ev, &mut upserts_ev);
 
@@ -236,7 +238,7 @@ impl Generation {
     ///
     /// Some of the tempids may be identified, so we also provide a map from tempid to a dense set
     /// of contiguous integer labels.
-    pub(crate) fn temp_ids_in_allocations(&self, schema: &Schema) -> errors::Result<BTreeMap<TempIdHandle, usize>> {
+    pub(crate) fn temp_ids_in_allocations(&self, schema: &Schema) -> Result<BTreeMap<TempIdHandle, usize>> {
         assert!(self.upserts_e.is_empty(), "All upserts should have been upserted, resolved, or moved to the allocated population!");
         assert!(self.upserts_ev.is_empty(), "All upserts should have been upserted, resolved, or moved to the allocated population!");
 
@@ -313,7 +315,7 @@ impl Generation {
 
     /// After evolution is complete, use the provided allocated entids to segment `self` into
     /// populations, each with no references to tempids.
-    pub(crate) fn into_final_populations(self, temp_id_map: &TempIdMap) -> errors::Result<FinalPopulations> {
+    pub(crate) fn into_final_populations(self, temp_id_map: &TempIdMap) -> Result<FinalPopulations> {
         assert!(self.upserts_e.is_empty());
         assert!(self.upserts_ev.is_empty());
 
@@ -329,21 +331,21 @@ impl Generation {
                     match (op, temp_id_map.get(&*t1), temp_id_map.get(&*t2)) {
                         (op, Some(&n1), Some(&n2)) => Term::AddOrRetract(op, n1, a, TypedValue::Ref(n2.0)),
                         (OpType::Add, _, _) => unreachable!(), // This is a coding error -- every tempid in a :db/add entity should resolve or be allocated.
-                        (OpType::Retract, _, _) => bail!(ErrorKind::NotYetImplemented(format!("[:db/retract ...] entity referenced tempid that did not upsert: one of {}, {}", t1, t2))),
+                        (OpType::Retract, _, _) => bail!(DbError::NotYetImplemented(format!("[:db/retract ...] entity referenced tempid that did not upsert: one of {}, {}", t1, t2))),
                     }
                 },
                 Term::AddOrRetract(op, Right(t), a, Left(v)) => {
                     match (op, temp_id_map.get(&*t)) {
                         (op, Some(&n)) => Term::AddOrRetract(op, n, a, v),
                         (OpType::Add, _) => unreachable!(), // This is a coding error.
-                        (OpType::Retract, _) => bail!(ErrorKind::NotYetImplemented(format!("[:db/retract ...] entity referenced tempid that did not upsert: {}", t))),
+                        (OpType::Retract, _) => bail!(DbError::NotYetImplemented(format!("[:db/retract ...] entity referenced tempid that did not upsert: {}", t))),
                     }
                 },
                 Term::AddOrRetract(op, Left(e), a, Right(t)) => {
                     match (op, temp_id_map.get(&*t)) {
                         (op, Some(&n)) => Term::AddOrRetract(op, e, a, TypedValue::Ref(n.0)),
                         (OpType::Add, _) => unreachable!(), // This is a coding error.
-                        (OpType::Retract, _) => bail!(ErrorKind::NotYetImplemented(format!("[:db/retract ...] entity referenced tempid that did not upsert: {}", t))),
+                        (OpType::Retract, _) => bail!(DbError::NotYetImplemented(format!("[:db/retract ...] entity referenced tempid that did not upsert: {}", t))),
                     }
                 },
                 Term::AddOrRetract(_, Left(_), _, Left(_)) => unreachable!(), // This is a coding error -- these should not be in allocations.

ffi/src/lib.rs

@@ -67,9 +67,12 @@
 //! propogation. These types have implemented [From](std::convert::From) such that conversion from the Rust type
 //! to the C type is as painless as possible.
 
+extern crate core;
 extern crate libc;
 extern crate mentat;
 
+use core::fmt::Display;
+
 use std::collections::{
     BTreeSet,
 };
@@ -204,7 +207,7 @@ pub struct ExternResult {
     pub err: *const c_char,
 }
 
-impl<T, E> From<Result<T, E>> for ExternResult where E: std::error::Error {
+impl<T, E> From<Result<T, E>> for ExternResult where E: Display {
     fn from(result: Result<T, E>) -> Self {
         match result {
             Ok(value) => {

parser-utils/src/lib.rs

@@ -13,8 +13,7 @@ extern crate edn;
 extern crate itertools;
 
 /// A `ValueParseError` is a `combine::primitives::ParseError`-alike that implements the `Debug`,
-/// `Display`, and `std::error::Error` traits.  In addition, it doesn't capture references, making
-/// it possible to store `ValueParseError` instances in local links with the `error-chain` crate.
+/// `Display`, and `std::error::Error` traits.  In addition, it doesn't capture references.
 ///
 /// This is achieved by wrapping slices of type `&'a [edn::Value]` in an owning type that implements
 /// `Display`; rather than introducing a newtype like `DisplayVec`, we re-use `edn::Value::Vector`.

query-algebrizer/Cargo.toml

@@ -4,7 +4,8 @@ version = "0.0.1"
 workspace = ".."
 
 [dependencies]
-error-chain = { git = "https://github.com/rnewman/error-chain", branch = "rnewman/sync" }
+failure = "0.1.1"
+failure_derive = "0.1.1"
 
 [dependencies.mentat_core]
 path = "../core"

query-algebrizer/src/clauses/convert.rs

@@ -28,7 +28,7 @@ use clauses::{
 };
 
 use errors::{
-    ErrorKind,
+    AlgebrizerError,
     Result,
 };
 
@@ -80,12 +80,12 @@ impl ValueTypes for FnArg {
 
                 &FnArg::Constant(NonIntegerConstant::BigInteger(_)) => {
                     // Not yet implemented.
-                    bail!(ErrorKind::UnsupportedArgument)
+                    bail!(AlgebrizerError::UnsupportedArgument)
                 },
 
                 // These don't make sense here. TODO: split FnArg into scalar and non-scalar…
                 &FnArg::Vector(_) |
-                &FnArg::SrcVar(_) => bail!(ErrorKind::UnsupportedArgument),
+                &FnArg::SrcVar(_) => bail!(AlgebrizerError::UnsupportedArgument),
 
                 // These are all straightforward.
                 &FnArg::Constant(NonIntegerConstant::Boolean(_)) => ValueTypeSet::of_one(ValueType::Boolean),
@@ -196,7 +196,7 @@ impl ConjoiningClauses {
             FnArg::Variable(in_var) => {
                 // TODO: technically you could ground an existing variable inside the query….
                 if !self.input_variables.contains(&in_var) {
-                    bail!(ErrorKind::UnboundVariable((*in_var.0).clone()));
+                    bail!(AlgebrizerError::UnboundVariable((*in_var.0).clone()))
                 }
                 match self.bound_value(&in_var) {
                     // The type is already known if it's a bound variable….
@@ -205,7 +205,7 @@ impl ConjoiningClauses {
                         // The variable is present in `:in`, but it hasn't yet been provided.
                         // This is a restriction we will eventually relax: we don't yet have a way
                         // to collect variables as part of a computed table or substitution.
-                        bail!(ErrorKind::UnboundVariable((*in_var.0).clone()))
+                        bail!(AlgebrizerError::UnboundVariable((*in_var.0).clone()))
                     },
                 }
             },
@@ -215,7 +215,7 @@ impl ConjoiningClauses {
 
             // These don't make sense here.
             FnArg::Vector(_) |
-            FnArg::SrcVar(_) => bail!(ErrorKind::InvalidGroundConstant),
+            FnArg::SrcVar(_) => bail!(AlgebrizerError::InvalidGroundConstant),
 
             // These are all straightforward.
             FnArg::Constant(NonIntegerConstant::Boolean(x)) => {

query-algebrizer/src/clauses/fulltext.rs

@@ -30,8 +30,9 @@ use clauses::{
 };
 
 use errors::{
+    AlgebrizerError,
     BindingError,
-    ErrorKind,
+    InvalidBinding,
     Result,
 };
 
@@ -53,17 +54,17 @@ impl ConjoiningClauses {
     #[allow(unused_variables)]
     pub(crate) fn apply_fulltext(&mut self, known: Known, where_fn: WhereFn) -> Result<()> {
         if where_fn.args.len() != 3 {
-            bail!(ErrorKind::InvalidNumberOfArguments(where_fn.operator.clone(), where_fn.args.len(), 3));
+            bail!(AlgebrizerError::InvalidNumberOfArguments(where_fn.operator.clone(), where_fn.args.len(), 3));
         }
 
         if where_fn.binding.is_empty() {
             // The binding must introduce at least one bound variable.
-            bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(), BindingError::NoBoundVariable));
+            bail!(InvalidBinding::new(where_fn.operator.clone(), BindingError::NoBoundVariable));
         }
 
         if !where_fn.binding.is_valid() {
             // The binding must not duplicate bound variables.
-            bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(), BindingError::RepeatedBoundVariable));
+            bail!(InvalidBinding::new(where_fn.operator.clone(), BindingError::RepeatedBoundVariable));
         }
 
         // We should have exactly four bindings. Destructure them now.
@@ -71,17 +72,18 @@ impl ConjoiningClauses {
             Binding::BindRel(bindings) => {
                 let bindings_count = bindings.len();
                 if bindings_count < 1 || bindings_count > 4 {
-                    bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(),
+                    bail!(InvalidBinding::new(where_fn.operator.clone(),
                         BindingError::InvalidNumberOfBindings {
                             number: bindings.len(),
                             expected: 4,
-                                                    }));
+                        })
+                    );
                 }
                 bindings
             },
             Binding::BindScalar(_) |
             Binding::BindTuple(_) |
-            Binding::BindColl(_) => bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(), BindingError::ExpectedBindRel)),
+            Binding::BindColl(_) => bail!(InvalidBinding::new(where_fn.operator.clone(), BindingError::ExpectedBindRel)),
         };
         let mut bindings = bindings.into_iter();
         let b_entity = bindings.next().unwrap();
@@ -94,7 +96,7 @@ impl ConjoiningClauses {
         // TODO: process source variables.
         match args.next().unwrap() {
             FnArg::SrcVar(SrcVar::DefaultSrc) => {},
-            _ => bail!(ErrorKind::InvalidArgument(where_fn.operator.clone(), "source variable", 0)),
+            _ => bail!(AlgebrizerError::InvalidArgument(where_fn.operator.clone(), "source variable", 0)),
         }
 
         let schema = known.schema;
@@ -114,10 +116,10 @@ impl ConjoiningClauses {
                 match self.bound_value(&v) {
                     Some(TypedValue::Ref(entid)) => Some(entid),
                     Some(tv) => {
-                        bail!(ErrorKind::InputTypeDisagreement(v.name().clone(), ValueType::Ref, tv.value_type()));
+                        bail!(AlgebrizerError::InputTypeDisagreement(v.name().clone(), ValueType::Ref, tv.value_type()))
                     },
                     None => {
-                        bail!(ErrorKind::UnboundVariable((*v.0).clone()));
+                        bail!(AlgebrizerError::UnboundVariable((*v.0).clone()))
                     }
                 }
             },
@@ -127,10 +129,10 @@ impl ConjoiningClauses {
         // An unknown ident, or an entity that isn't present in the store, or isn't a fulltext
         // attribute, is likely enough to be a coding error that we choose to bail instead of
         // marking the pattern as known-empty.
-        let a = a.ok_or(ErrorKind::InvalidArgument(where_fn.operator.clone(), "attribute", 1))?;
+        let a = a.ok_or(AlgebrizerError::InvalidArgument(where_fn.operator.clone(), "attribute", 1))?;
         let attribute = schema.attribute_for_entid(a)
                               .cloned()
-                              .ok_or(ErrorKind::InvalidArgument(where_fn.operator.clone(),
+                              .ok_or(AlgebrizerError::InvalidArgument(where_fn.operator.clone(),
                                                                 "attribute", 1))?;
 
         if !attribute.fulltext {
@@ -169,18 +171,18 @@ impl ConjoiningClauses {
             FnArg::Variable(in_var) => {
                 match self.bound_value(&in_var) {
                     Some(t @ TypedValue::String(_)) => Either::Left(t),
-                    Some(_) => bail!(ErrorKind::InvalidArgument(where_fn.operator.clone(), "string", 2)),
+                    Some(_) => bail!(AlgebrizerError::InvalidArgument(where_fn.operator.clone(), "string", 2)),
                     None => {
                         // Regardless of whether we'll be providing a string later, or the value
                         // comes from a column, it must be a string.
                         if self.known_type(&in_var) != Some(ValueType::String) {
-                            bail!(ErrorKind::InvalidArgument(where_fn.operator.clone(), "string", 2));
+                            bail!(AlgebrizerError::InvalidArgument(where_fn.operator.clone(), "string", 2))
                         }
 
                         if self.input_variables.contains(&in_var) {
                             // Sorry, we haven't implemented late binding.
                             // TODO: implement this.
-                            bail!(ErrorKind::UnboundVariable((*in_var.0).clone()));
+                            bail!(AlgebrizerError::UnboundVariable((*in_var.0).clone()))
                         } else {
                             // It must be bound earlier in the query. We already established that
                             // it must be a string column.
@@ -189,13 +191,13 @@ impl ConjoiningClauses {
                                                        .and_then(|bindings| bindings.get(0).cloned()) {
                                 Either::Right(binding)
                             } else {
-                                bail!(ErrorKind::UnboundVariable((*in_var.0).clone()));
+                                bail!(AlgebrizerError::UnboundVariable((*in_var.0).clone()))
                             }
                         }
                     },
                 }
             },
-            _ => bail!(ErrorKind::InvalidArgument(where_fn.operator.clone(), "string", 2)),
+            _ => bail!(AlgebrizerError::InvalidArgument(where_fn.operator.clone(), "string", 2)),
         };
 
         let qv = match search {
@@ -244,7 +246,7 @@ impl ConjoiningClauses {
 
             // We do not allow the score to be bound.
             if self.value_bindings.contains_key(var) || self.input_variables.contains(var) {
-                bail!(ErrorKind::InvalidBinding(var.name(), BindingError::UnexpectedBinding));
+                bail!(InvalidBinding::new(var.name(), BindingError::UnexpectedBinding));
             }
 
             // We bind the value ourselves. This handily takes care of substituting into existing uses.

query-algebrizer/src/clauses/ground.rs

@@ -31,8 +31,9 @@ use clauses::{
 use clauses::convert::ValueConversion;
 
 use errors::{
+    AlgebrizerError,
     BindingError,
-    ErrorKind,
+    InvalidBinding,
     Result,
 };
 
@@ -117,19 +118,19 @@ impl ConjoiningClauses {
 
     pub(crate) fn apply_ground(&mut self, known: Known, where_fn: WhereFn) -> Result<()> {
         if where_fn.args.len() != 1 {
-            bail!(ErrorKind::InvalidNumberOfArguments(where_fn.operator.clone(), where_fn.args.len(), 1));
+            bail!(AlgebrizerError::InvalidNumberOfArguments(where_fn.operator.clone(), where_fn.args.len(), 1));
         }
 
         let mut args = where_fn.args.into_iter();
 
         if where_fn.binding.is_empty() {
             // The binding must introduce at least one bound variable.
-            bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(), BindingError::NoBoundVariable));
+            bail!(InvalidBinding::new(where_fn.operator.clone(), BindingError::NoBoundVariable));
         }
 
         if !where_fn.binding.is_valid() {
             // The binding must not duplicate bound variables.
-            bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(), BindingError::RepeatedBoundVariable));
+            bail!(InvalidBinding::new(where_fn.operator.clone(), BindingError::RepeatedBoundVariable));
         }
 
         let schema = known.schema;
@@ -145,7 +146,7 @@ impl ConjoiningClauses {
                 // Just the same, but we bind more than one column at a time.
                 if children.len() != places.len() {
                     // Number of arguments don't match the number of values. TODO: better error message.
-                    bail!(ErrorKind::GroundBindingsMismatch);
+                    bail!(AlgebrizerError::GroundBindingsMismatch)
                 }
                 for (place, arg) in places.into_iter().zip(children.into_iter()) {
                     self.apply_ground_place(schema, place, arg)?  // TODO: short-circuit on impossible.
@@ -159,7 +160,7 @@ impl ConjoiningClauses {
             // are all in a single structure. That makes it substantially simpler!
             (Binding::BindColl(var), FnArg::Vector(children)) => {
                 if children.is_empty() {
-                    bail!(ErrorKind::InvalidGroundConstant);
+                    bail!(AlgebrizerError::InvalidGroundConstant)
                 }
 
                 // Turn a collection of arguments into a Vec of `TypedValue`s of the same type.
@@ -177,7 +178,7 @@ impl ConjoiningClauses {
                                                  if accumulated_types.insert(tv.value_type()) &&
                                                     !accumulated_types.is_unit() {
                                                      // Values not all of the same type.
-                                                     Some(Err(ErrorKind::InvalidGroundConstant.into()))
+                                                     Some(Err(AlgebrizerError::InvalidGroundConstant.into()))
                                                  } else {
                                                      Some(Ok(tv))
                                                  }
@@ -208,7 +209,7 @@ impl ConjoiningClauses {
 
             (Binding::BindRel(places), FnArg::Vector(rows)) => {
                 if rows.is_empty() {
-                    bail!(ErrorKind::InvalidGroundConstant);
+                    bail!(AlgebrizerError::InvalidGroundConstant)
                 }
 
                 // Grab the known types to which these args must conform, and track
@@ -229,7 +230,7 @@ impl ConjoiningClauses {
 
                 if expected_width == 0 {
                     // They can't all be placeholders.
-                    bail!(ErrorKind::InvalidGroundConstant);
+                    bail!(AlgebrizerError::InvalidGroundConstant)
                 }
 
                 // Accumulate values into `matrix` and types into `a_t_f_c`.
@@ -245,7 +246,7 @@ impl ConjoiningClauses {
                         FnArg::Vector(cols) => {
                             // Make sure that every row is the same length.
                             if cols.len() != full_width {
-                                bail!(ErrorKind::InvalidGroundConstant);
+                                bail!(AlgebrizerError::InvalidGroundConstant)
                             }
 
                             // TODO: don't accumulate twice.
@@ -280,13 +281,13 @@ impl ConjoiningClauses {
                                 let inserted = acc.insert(val.value_type());
                                 if inserted && !acc.is_unit() {
                                     // Heterogeneous types.
-                                    bail!(ErrorKind::InvalidGroundConstant);
+                                    bail!(AlgebrizerError::InvalidGroundConstant)
                                 }
                                 matrix.push(val);
                             }
 
                         },
-                        _ => bail!(ErrorKind::InvalidGroundConstant),
+                        _ => bail!(AlgebrizerError::InvalidGroundConstant),
                     }
                 }
 
@@ -312,7 +313,7 @@ impl ConjoiningClauses {
                 self.collect_named_bindings(schema, names, types, matrix);
                 Ok(())
             },
-            (_, _) => bail!(ErrorKind::InvalidGroundConstant),
+            (_, _) => bail!(AlgebrizerError::InvalidGroundConstant),
         }
     }
 }

query-algebrizer/src/clauses/inputs.rs

@@ -20,7 +20,7 @@ use mentat_query::{
 };
 
 use errors::{
-    ErrorKind,
+    AlgebrizerError,
     Result,
 };
 
@@ -72,7 +72,7 @@ impl QueryInputs {
             let old = types.insert(var.clone(), t);
             if let Some(old) = old {
                 if old != t {
-                    bail!(ErrorKind::InputTypeDisagreement(var.name(), old, t));
+                    bail!(AlgebrizerError::InputTypeDisagreement(var.name(), old, t));
                 }
             }
         }

query-algebrizer/src/clauses/mod.rs

@@ -53,8 +53,7 @@ use mentat_query::{
 };
 
 use errors::{
-    Error,
-    ErrorKind,
+    AlgebrizerError,
     Result,
 };
 
@@ -1014,7 +1013,7 @@ impl ConjoiningClauses {
 
             let qa = self.extracted_types
                          .get(&var)
-                         .ok_or_else(|| Error::from_kind(ErrorKind::UnboundVariable(var.name())))?;
+                         .ok_or_else(|| AlgebrizerError::UnboundVariable(var.name()))?;
             self.wheres.add_intersection(ColumnConstraint::HasTypes {
                 value: qa.0.clone(),
                 value_types: types,

query-algebrizer/src/clauses/not.rs

@@ -17,7 +17,7 @@ use mentat_query::{
 use clauses::ConjoiningClauses;
 
 use errors::{
-    ErrorKind,
+    AlgebrizerError,
     Result,
 };
 
@@ -45,7 +45,7 @@ impl ConjoiningClauses {
                 let col = self.column_bindings.get(&v).unwrap()[0].clone();
                 template.column_bindings.insert(v.clone(), vec![col]);
             } else {
-                bail!(ErrorKind::UnboundVariable(v.name()));
+                bail!(AlgebrizerError::UnboundVariable(v.name()));
             }
         }
 
@@ -111,8 +111,7 @@ mod testing {
     };
 
     use errors::{
-        Error,
-        ErrorKind,
+        AlgebrizerError,
     };
 
     use types::{
@@ -553,10 +552,9 @@ mod testing {
          :in ?y
          :where (not [?x :foo/knows ?y])]"#;
         let parsed = parse_find_string(query).expect("parse failed");
-        let err = algebrize(known, parsed).err();
-        assert!(err.is_some());
-         match err.unwrap() {
-            Error(ErrorKind::UnboundVariable(var), _) => { assert_eq!(var, PlainSymbol("?x".to_string())); },
+        let err = algebrize(known, parsed).expect_err("algebrization should have failed");
+        match err.downcast().expect("expected AlgebrizerError") {
+            AlgebrizerError::UnboundVariable(var) => { assert_eq!(var, PlainSymbol("?x".to_string())); },
             x => panic!("expected Unbound Variable error, got {:?}", x),
         }
     }

query-algebrizer/src/clauses/predicate.rs

@@ -26,8 +26,8 @@ use clauses::ConjoiningClauses;
 use clauses::convert::ValueTypes;
 
 use errors::{
+    AlgebrizerError,
     Result,
-    ErrorKind,
 };
 
 use types::{
@@ -53,7 +53,7 @@ impl ConjoiningClauses {
         if let Some(op) = Inequality::from_datalog_operator(predicate.operator.0.as_str()) {
             self.apply_inequality(known, op, predicate)
         } else {
-            bail!(ErrorKind::UnknownFunction(predicate.operator.clone()))
+            bail!(AlgebrizerError::UnknownFunction(predicate.operator.clone()))
         }
     }
 
@@ -69,7 +69,7 @@ impl ConjoiningClauses {
     pub(crate) fn apply_type_anno(&mut self, anno: &TypeAnnotation) -> Result<()> {
         match ValueType::from_keyword(&anno.value_type) {
             Some(value_type) => self.add_type_requirement(anno.variable.clone(), ValueTypeSet::of_one(value_type)),
-            None => bail!(ErrorKind::InvalidArgumentType(PlainSymbol::plain("type"), ValueTypeSet::any(), 2)),
+            None => bail!(AlgebrizerError::InvalidArgumentType(PlainSymbol::plain("type"), ValueTypeSet::any(), 2)),
         }
         Ok(())
     }
@@ -80,7 +80,7 @@ impl ConjoiningClauses {
     /// - Accumulates an `Inequality` constraint into the `wheres` list.
     pub(crate) fn apply_inequality(&mut self, known: Known, comparison: Inequality, predicate: Predicate) -> Result<()> {
         if predicate.args.len() != 2 {
-            bail!(ErrorKind::InvalidNumberOfArguments(predicate.operator.clone(), predicate.args.len(), 2));
+            bail!(AlgebrizerError::InvalidNumberOfArguments(predicate.operator.clone(), predicate.args.len(), 2));
         }
 
         // Go from arguments -- parser output -- to columns or values.
@@ -97,13 +97,13 @@ impl ConjoiningClauses {
         let mut left_types = self.potential_types(known.schema, &left)?
                                  .intersection(&supported_types);
         if left_types.is_empty() {
-            bail!(ErrorKind::InvalidArgumentType(predicate.operator.clone(), supported_types, 0));
+            bail!(AlgebrizerError::InvalidArgumentType(predicate.operator.clone(), supported_types, 0));
         }
 
         let mut right_types = self.potential_types(known.schema, &right)?
                                   .intersection(&supported_types);
         if right_types.is_empty() {
-            bail!(ErrorKind::InvalidArgumentType(predicate.operator.clone(), supported_types, 1));
+            bail!(AlgebrizerError::InvalidArgumentType(predicate.operator.clone(), supported_types, 1));
         }
 
         // We would like to allow longs to compare to doubles.
@@ -150,7 +150,7 @@ impl ConjoiningClauses {
             left_v = self.resolve_ref_argument(known.schema, &predicate.operator, 0, left)?;
             right_v = self.resolve_ref_argument(known.schema, &predicate.operator, 1, right)?;
         } else {
-            bail!(ErrorKind::InvalidArgumentType(predicate.operator.clone(), supported_types, 0));
+            bail!(AlgebrizerError::InvalidArgumentType(predicate.operator.clone(), supported_types, 0));
         }
 
         // These arguments must be variables or instant/numeric constants.

query-algebrizer/src/clauses/resolve.rs

@@ -24,9 +24,8 @@ use mentat_query::{
 use clauses::ConjoiningClauses;
 
 use errors::{
+    AlgebrizerError,
     Result,
-    Error,
-    ErrorKind,
 };
 
 use types::{
@@ -50,14 +49,14 @@ impl ConjoiningClauses {
                     if v.value_type().is_numeric() {
                         Ok(QueryValue::TypedValue(v))
                     } else {
-                        bail!(ErrorKind::InputTypeDisagreement(var.name().clone(), ValueType::Long, v.value_type()));
+                        bail!(AlgebrizerError::InputTypeDisagreement(var.name().clone(), ValueType::Long, v.value_type()))
                     }
                 } else {
                     self.constrain_var_to_numeric(var.clone());
                     self.column_bindings
                         .get(&var)
                         .and_then(|cols| cols.first().map(|col| QueryValue::Column(col.clone())))
-                        .ok_or_else(|| Error::from_kind(ErrorKind::UnboundVariable(var.name())))
+                        .ok_or_else(|| AlgebrizerError::UnboundVariable(var.name()).into())
                 }
             },
             // Can't be an entid.
@@ -71,7 +70,7 @@ impl ConjoiningClauses {
             Constant(NonIntegerConstant::BigInteger(_)) |
             Vector(_) => {
                 self.mark_known_empty(EmptyBecause::NonNumericArgument);
-                bail!(ErrorKind::InvalidArgument(function.clone(), "numeric", position));
+                bail!(AlgebrizerError::InvalidArgument(function.clone(), "numeric", position))
             },
             Constant(NonIntegerConstant::Float(f)) => Ok(QueryValue::TypedValue(TypedValue::Double(f))),
         }
@@ -84,13 +83,13 @@ impl ConjoiningClauses {
             FnArg::Variable(var) => {
                 match self.bound_value(&var) {
                     Some(TypedValue::Instant(v)) => Ok(QueryValue::TypedValue(TypedValue::Instant(v))),
-                    Some(v) => bail!(ErrorKind::InputTypeDisagreement(var.name().clone(), ValueType::Instant, v.value_type())),
+                    Some(v) => bail!(AlgebrizerError::InputTypeDisagreement(var.name().clone(), ValueType::Instant, v.value_type())),
                     None => {
                         self.constrain_var_to_type(var.clone(), ValueType::Instant);
                         self.column_bindings
                             .get(&var)
                             .and_then(|cols| cols.first().map(|col| QueryValue::Column(col.clone())))
-                            .ok_or_else(|| Error::from_kind(ErrorKind::UnboundVariable(var.name())))
+                            .ok_or_else(|| AlgebrizerError::UnboundVariable(var.name()).into())
                     },
                 }
             },
@@ -109,7 +108,7 @@ impl ConjoiningClauses {
             Constant(NonIntegerConstant::BigInteger(_)) |
             Vector(_) => {
                 self.mark_known_empty(EmptyBecause::NonInstantArgument);
-                bail!(ErrorKind::InvalidArgumentType(function.clone(), ValueType::Instant.into(), position));
+                bail!(AlgebrizerError::InvalidArgumentType(function.clone(), ValueType::Instant.into(), position))
             },
         }
     }
@@ -128,14 +127,14 @@ impl ConjoiningClauses {
                     self.column_bindings
                         .get(&var)
                         .and_then(|cols| cols.first().map(|col| QueryValue::Column(col.clone())))
-                        .ok_or_else(|| Error::from_kind(ErrorKind::UnboundVariable(var.name())))
+                        .ok_or_else(|| AlgebrizerError::UnboundVariable(var.name()).into())
                 }
             },
             EntidOrInteger(i) => Ok(QueryValue::TypedValue(TypedValue::Ref(i))),
             IdentOrKeyword(i) => {
                 schema.get_entid(&i)
                       .map(|known_entid| QueryValue::Entid(known_entid.into()))
-                      .ok_or_else(|| Error::from_kind(ErrorKind::UnrecognizedIdent(i.to_string())))
+                      .ok_or_else(|| AlgebrizerError::UnrecognizedIdent(i.to_string()).into())
             },
             Constant(NonIntegerConstant::Boolean(_)) |
             Constant(NonIntegerConstant::Float(_)) |
@@ -146,7 +145,7 @@ impl ConjoiningClauses {
             SrcVar(_) |
             Vector(_) => {
                 self.mark_known_empty(EmptyBecause::NonEntityArgument);
-                bail!(ErrorKind::InvalidArgumentType(function.clone(), ValueType::Ref.into(), position));
+                bail!(AlgebrizerError::InvalidArgumentType(function.clone(), ValueType::Ref.into(), position))
             },
 
         }
@@ -173,7 +172,7 @@ impl ConjoiningClauses {
                         self.column_bindings
                             .get(&var)
                             .and_then(|cols| cols.first().map(|col| QueryValue::Column(col.clone())))
-                            .ok_or_else(|| Error::from_kind(ErrorKind::UnboundVariable(var.name())))
+                            .ok_or_else(|| AlgebrizerError::UnboundVariable(var.name()).into())
                     },
                 }
             },

query-algebrizer/src/clauses/tx_log_api.rs

@@ -25,8 +25,9 @@ use clauses::{
 };
 
 use errors::{
+    AlgebrizerError,
     BindingError,
-    ErrorKind,
+    InvalidBinding,
     Result,
 };
 
@@ -60,17 +61,17 @@ impl ConjoiningClauses {
     // transactions that impact one of the given attributes.
     pub(crate) fn apply_tx_ids(&mut self, known: Known, where_fn: WhereFn) -> Result<()> {
         if where_fn.args.len() != 3 {
-            bail!(ErrorKind::InvalidNumberOfArguments(where_fn.operator.clone(), where_fn.args.len(), 3));
+            bail!(AlgebrizerError::InvalidNumberOfArguments(where_fn.operator.clone(), where_fn.args.len(), 3));
         }
 
         if where_fn.binding.is_empty() {
             // The binding must introduce at least one bound variable.
-            bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(), BindingError::NoBoundVariable));
+            bail!(InvalidBinding::new(where_fn.operator.clone(), BindingError::NoBoundVariable));
         }
 
         if !where_fn.binding.is_valid() {
             // The binding must not duplicate bound variables.
-            bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(), BindingError::RepeatedBoundVariable));
+            bail!(InvalidBinding::new(where_fn.operator.clone(), BindingError::RepeatedBoundVariable));
         }
 
         // We should have exactly one binding. Destructure it now.
@@ -78,7 +79,7 @@ impl ConjoiningClauses {
             Binding::BindRel(bindings) => {
                 let bindings_count = bindings.len();
                 if bindings_count != 1 {
-                    bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(),
+                    bail!(InvalidBinding::new(where_fn.operator.clone(),
                                                     BindingError::InvalidNumberOfBindings {
                                                         number: bindings_count,
                                                         expected: 1,
@@ -92,7 +93,7 @@ impl ConjoiningClauses {
             Binding::BindColl(v) => v,
             Binding::BindScalar(_) |
             Binding::BindTuple(_) => {
-                bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(), BindingError::ExpectedBindRelOrBindColl))
+                bail!(InvalidBinding::new(where_fn.operator.clone(), BindingError::ExpectedBindRelOrBindColl))
             },
         };
 
@@ -101,7 +102,7 @@ impl ConjoiningClauses {
         // TODO: process source variables.
         match args.next().unwrap() {
             FnArg::SrcVar(SrcVar::DefaultSrc) => {},
-            _ => bail!(ErrorKind::InvalidArgument(where_fn.operator.clone(), "source variable", 0)),
+            _ => bail!(AlgebrizerError::InvalidArgument(where_fn.operator.clone(), "source variable", 0)),
         }
 
         let tx1 = self.resolve_tx_argument(&known.schema, &where_fn.operator, 1, args.next().unwrap())?;
@@ -138,17 +139,17 @@ impl ConjoiningClauses {
 
     pub(crate) fn apply_tx_data(&mut self, known: Known, where_fn: WhereFn) -> Result<()> {
         if where_fn.args.len() != 2 {
-            bail!(ErrorKind::InvalidNumberOfArguments(where_fn.operator.clone(), where_fn.args.len(), 2));
+            bail!(AlgebrizerError::InvalidNumberOfArguments(where_fn.operator.clone(), where_fn.args.len(), 2));
         }
 
         if where_fn.binding.is_empty() {
             // The binding must introduce at least one bound variable.
-            bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(), BindingError::NoBoundVariable));
+            bail!(InvalidBinding::new(where_fn.operator.clone(), BindingError::NoBoundVariable));
         }
 
         if !where_fn.binding.is_valid() {
             // The binding must not duplicate bound variables.
-            bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(), BindingError::RepeatedBoundVariable));
+            bail!(InvalidBinding::new(where_fn.operator.clone(), BindingError::RepeatedBoundVariable));
         }
 
         // We should have at most five bindings. Destructure them now.
@@ -156,7 +157,7 @@ impl ConjoiningClauses {
             Binding::BindRel(bindings) => {
                 let bindings_count = bindings.len();
                 if bindings_count < 1 || bindings_count > 5 {
-                    bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(),
+                    bail!(InvalidBinding::new(where_fn.operator.clone(),
                                                     BindingError::InvalidNumberOfBindings {
                                                         number: bindings.len(),
                                                         expected: 5,
@@ -166,7 +167,7 @@ impl ConjoiningClauses {
             },
             Binding::BindScalar(_) |
             Binding::BindTuple(_) |
-            Binding::BindColl(_) => bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(), BindingError::ExpectedBindRel)),
+            Binding::BindColl(_) => bail!(InvalidBinding::new(where_fn.operator.clone(), BindingError::ExpectedBindRel)),
         };
         let mut bindings = bindings.into_iter();
         let b_e = bindings.next().unwrap_or(VariableOrPlaceholder::Placeholder);
@@ -180,7 +181,7 @@ impl ConjoiningClauses {
         // TODO: process source variables.
         match args.next().unwrap() {
             FnArg::SrcVar(SrcVar::DefaultSrc) => {},
-            _ => bail!(ErrorKind::InvalidArgument(where_fn.operator.clone(), "source variable", 0)),
+            _ => bail!(AlgebrizerError::InvalidArgument(where_fn.operator.clone(), "source variable", 0)),
         }
 
         let tx = self.resolve_tx_argument(&known.schema, &where_fn.operator, 1, args.next().unwrap())?;

query-algebrizer/src/clauses/where_fn.rs

@@ -17,7 +17,7 @@ use clauses::{
 };
 
 use errors::{
-    ErrorKind,
+    AlgebrizerError,
     Result,
 };
 
@@ -39,7 +39,7 @@ impl ConjoiningClauses {
             "ground" => self.apply_ground(known, where_fn),
             "tx-data" => self.apply_tx_data(known, where_fn),
             "tx-ids" => self.apply_tx_ids(known, where_fn),
-            _ => bail!(ErrorKind::UnknownFunction(where_fn.operator.clone())),
+            _ => bail!(AlgebrizerError::UnknownFunction(where_fn.operator.clone())),
         }
     }
 }

query-algebrizer/src/errors.rs

@@ -10,8 +10,18 @@
 
 extern crate mentat_query;
 
+use std; // To refer to std::result::Result.
+use std::fmt;
+use std::fmt::Display;
+
+use failure::{
+    Backtrace,
+    Context,
+    Error,
+    Fail,
+};
+
 use mentat_core::{
-    EdnParseError,
     ValueType,
     ValueTypeSet,
 };
@@ -20,7 +30,53 @@ use self::mentat_query::{
     PlainSymbol,
 };
 
-#[derive(Clone, Debug, Eq, PartialEq)]
+pub type Result<T> = std::result::Result<T, Error>;
+
+#[macro_export]
+macro_rules! bail {
+    ($e:expr) => (
+        return Err($e.into());
+    )
+}
+
+#[derive(Debug)]
+pub struct InvalidBinding {
+    pub function: PlainSymbol,
+    pub inner: Context<BindingError>
+}
+
+impl InvalidBinding {
+    pub fn new(function: PlainSymbol, inner: BindingError) -> InvalidBinding {
+        InvalidBinding {
+            function: function,
+            inner: Context::new(inner)
+        }
+    }
+}
+
+impl Fail for InvalidBinding {
+    fn cause(&self) -> Option<&Fail> {
+        self.inner.cause()
+    }
+
+    fn backtrace(&self) -> Option<&Backtrace> {
+        self.inner.backtrace()
+    }
+}
+
+impl Display for InvalidBinding {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "invalid binding for {}: {:?}", self.function, self.inner)
+    }
+}
+
+impl Display for BindingError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "BindingError: {:?}", self)
+    }
+}
+
+#[derive(Clone, Debug, Eq, PartialEq, Fail)]
 pub enum BindingError {
     NoBoundVariable,
     UnexpectedBinding,
@@ -40,98 +96,52 @@ pub enum BindingError {
     InvalidNumberOfBindings { number: usize, expected: usize },
 }
 
-error_chain! {
-    types {
-        Error, ErrorKind, ResultExt, Result;
-    }
+#[derive(Debug, Fail)]
+pub enum AlgebrizerError {
+    #[fail(display = "{} var {} is duplicated", _0, _1)]
+    DuplicateVariableError(PlainSymbol, &'static str),
 
-    foreign_links {
-        EdnParseError(EdnParseError);
-    }
+    #[fail(display = "unexpected FnArg")]
+    UnsupportedArgument,
 
-    errors {
-        UnsupportedArgument {
-            description("unexpected FnArg")
-            display("unexpected FnArg")
-        }
+    #[fail(display = "value of type {} provided for var {}, expected {}", _0, _1, _2)]
+    InputTypeDisagreement(PlainSymbol, ValueType, ValueType),
 
-        InputTypeDisagreement(var: PlainSymbol, declared: ValueType, provided: ValueType) {
-            description("input type disagreement")
-            display("value of type {} provided for var {}, expected {}", provided, var, declared)
-        }
+    #[fail(display = "invalid number of arguments to {}: expected {}, got {}.", _0, _1, _2)]
+    InvalidNumberOfArguments(PlainSymbol, usize, usize),
 
-        UnrecognizedIdent(ident: String) {
-            description("no entid found for ident")
-            display("no entid found for ident: {}", ident)
-        }
+    #[fail(display = "invalid argument to {}: expected {} in position {}.", _0, _1, _2)]
+    InvalidArgument(PlainSymbol, &'static str, usize),
 
-        UnknownFunction(name: PlainSymbol) {
-            description("no such function")
-            display("no function named {}", name)
-        }
+    #[fail(display = "invalid argument to {}: expected one of {:?} in position {}.", _0, _1, _2)]
+    InvalidArgumentType(PlainSymbol, ValueTypeSet, usize),
 
-        InvalidNumberOfArguments(function: PlainSymbol, number: usize, expected: usize) {
-            description("invalid number of arguments")
-            display("invalid number of arguments to {}: expected {}, got {}.", function, expected, number)
-        }
-
-        UnboundVariable(name: PlainSymbol) {
-            description("unbound variable in order clause or function call")
-            display("unbound variable: {}", name)
-        }
-
-        InvalidBinding(function: PlainSymbol, binding_error: BindingError) {
-            description("invalid binding")
-            display("invalid binding for {}: {:?}.", function, binding_error)
-        }
-
-        GroundBindingsMismatch {
-            description("mismatched bindings in ground")
-            display("mismatched bindings in ground")
-        }
-
-        InvalidGroundConstant {
     // TODO: flesh this out.
-            description("invalid expression in ground constant")
-            display("invalid expression in ground constant")
-        }
+    #[fail(display = "invalid expression in ground constant")]
+    InvalidGroundConstant,
 
-        InvalidArgument(function: PlainSymbol, expected: &'static str, position: usize) {
-            description("invalid argument")
-            display("invalid argument to {}: expected {} in position {}.", function, expected, position)
-        }
+    #[fail(display = "invalid limit {} of type {}: expected natural number.", _0, _1)]
+    InvalidLimit(String, ValueType),
 
-        InvalidArgumentType(function: PlainSymbol, expected_types: ValueTypeSet, position: usize) {
-            description("invalid argument")
-            display("invalid argument to {}: expected one of {:?} in position {}.", function, expected_types, position)
-        }
+    #[fail(display = "mismatched bindings in ground")]
+    GroundBindingsMismatch,
 
-        InvalidLimit(val: String, kind: ValueType) {
-            description("invalid limit")
-            display("invalid limit {} of type {}: expected natural number.", val, kind)
-        }
+    #[fail(display = "no entid found for ident: {}", _0)]
+    UnrecognizedIdent(String),
+
+    #[fail(display = "no function named {}", _0)]
+    UnknownFunction(PlainSymbol),
+
+    #[fail(display = ":limit var {} not present in :in", _0)]
+    UnknownLimitVar(PlainSymbol),
+
+    #[fail(display = "unbound variable {} in order clause or function call", _0)]
+    UnboundVariable(PlainSymbol),
 
-        NonMatchingVariablesInOrClause {
     // TODO: flesh out.
-            description("non-matching variables in 'or' clause")
-            display("non-matching variables in 'or' clause")
-        }
+    #[fail(display = "non-matching variables in 'or' clause")]
+    NonMatchingVariablesInOrClause,
 
-        NonMatchingVariablesInNotClause {
-            // TODO: flesh out.
-            description("non-matching variables in 'not' clause")
-            display("non-matching variables in 'not' clause")
-        }
-
-        DuplicateVariableError(name: PlainSymbol, clause: &'static str)  {
-            description("duplicate variables")
-            display("{} var {} is duplicated", clause, name)
-        }
-
-        UnknownLimitVar(name: PlainSymbol) {
-            description(":limit var not present in :in")
-            display(":limit var {} not present in :in", name)
-        }
-    }
+    #[fail(display = "non-matching variables in 'not' clause")]
+    NonMatchingVariablesInNotClause,
 }
-

query-algebrizer/src/lib.rs

@@ -8,10 +8,9 @@
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
 
-#![recursion_limit="128"]
+extern crate failure;
 
-#[macro_use]
-extern crate error_chain;
+#[macro_use] extern crate failure_derive;
 
 extern crate mentat_core;
 extern crate mentat_query;
@@ -20,6 +19,7 @@ use std::collections::BTreeSet;
 use std::ops::Sub;
 use std::rc::Rc;
 
+#[macro_use]
 mod errors;
 mod types;
 mod validate;
@@ -48,10 +48,10 @@ use mentat_query::{
 };
 
 pub use errors::{
+    AlgebrizerError,
     BindingError,
-    Error,
-    ErrorKind,
     Result,
+    InvalidBinding,
 };
 
 pub use clauses::{
@@ -216,7 +216,7 @@ fn validate_and_simplify_order(cc: &ConjoiningClauses, order: Option<Vec<Order>>
 
                 // Fail if the var isn't bound by the query.
                 if !cc.column_bindings.contains_key(&var) {
-                    bail!(ErrorKind::UnboundVariable(var.name()));
+                    bail!(AlgebrizerError::UnboundVariable(var.name()))
                 }
 
                 // Otherwise, determine if we also need to order by type…
@@ -242,14 +242,14 @@ fn simplify_limit(mut query: AlgebraicQuery) -> Result<AlgebraicQuery> {
                     Some(TypedValue::Long(n)) => {
                         if n <= 0 {
                             // User-specified limits should always be natural numbers (> 0).
-                            bail!(ErrorKind::InvalidLimit(n.to_string(), ValueType::Long));
+                            bail!(AlgebrizerError::InvalidLimit(n.to_string(), ValueType::Long))
                         } else {
                             Some(Limit::Fixed(n as u64))
                         }
                     },
                     Some(val) => {
                         // Same.
-                        bail!(ErrorKind::InvalidLimit(format!("{:?}", val), val.value_type()));
+                        bail!(AlgebrizerError::InvalidLimit(format!("{:?}", val), val.value_type()))
                     },
                     None => {
                         // We know that the limit variable is mentioned in `:in`.
@@ -357,7 +357,7 @@ impl FindQuery {
 
             for var in parsed.in_vars.into_iter() {
                 if !set.insert(var.clone()) {
-                    bail!(ErrorKind::DuplicateVariableError(var.name(), ":in"));
+                    bail!(AlgebrizerError::DuplicateVariableError(var.name(), ":in"));
                 }
             }
 
@@ -369,7 +369,7 @@ impl FindQuery {
 
             for var in parsed.with.into_iter() {
                 if !set.insert(var.clone()) {
-                    bail!(ErrorKind::DuplicateVariableError(var.name(), ":with"));
+                    bail!(AlgebrizerError::DuplicateVariableError(var.name(), ":with"));
                 }
             }
 
@@ -379,7 +379,7 @@ impl FindQuery {
         // Make sure that if we have `:limit ?x`, `?x` appears in `:in`.
         if let Limit::Variable(ref v) = parsed.limit {
             if !in_vars.contains(v) {
-                bail!(ErrorKind::UnknownLimitVar(v.name()));
+                bail!(AlgebrizerError::UnknownLimitVar(v.name()));
             }
         }
 

query-algebrizer/src/validate.rs

@@ -19,7 +19,7 @@ use mentat_query::{
 };
 
 use errors::{
-    ErrorKind,
+    AlgebrizerError,
     Result,
 };
 
@@ -56,7 +56,7 @@ pub(crate) fn validate_or_join(or_join: &OrJoin) -> Result<()> {
                 let template = clauses.next().unwrap().collect_mentioned_variables();
                 for clause in clauses {
                     if template != clause.collect_mentioned_variables() {
-                        bail!(ErrorKind::NonMatchingVariablesInOrClause);
+                        bail!(AlgebrizerError::NonMatchingVariablesInOrClause)
                     }
                 }
                 Ok(())
@@ -67,7 +67,7 @@ pub(crate) fn validate_or_join(or_join: &OrJoin) -> Result<()> {
             let var_set: BTreeSet<Variable> = vars.iter().cloned().collect();
             for clause in &or_join.clauses {
                 if !var_set.is_subset(&clause.collect_mentioned_variables()) {
-                    bail!(ErrorKind::NonMatchingVariablesInOrClause);
+                    bail!(AlgebrizerError::NonMatchingVariablesInOrClause)
                 }
             }
             Ok(())
@@ -85,7 +85,7 @@ pub(crate) fn validate_not_join(not_join: &NotJoin) -> Result<()> {
             // The joined vars must each appear somewhere in the clause's mentioned variables.
             let var_set: BTreeSet<Variable> = vars.iter().cloned().collect();
             if !var_set.is_subset(&not_join.collect_mentioned_variables()) {
-                bail!(ErrorKind::NonMatchingVariablesInNotClause);
+                bail!(AlgebrizerError::NonMatchingVariablesInNotClause)
             }
             Ok(())
         },

query-algebrizer/tests/ground.rs

@@ -30,10 +30,10 @@ use mentat_query::{
 };
 
 use mentat_query_algebrizer::{
+    AlgebrizerError,
     BindingError,
     ComputedTable,
-    Error,
-    ErrorKind,
+    InvalidBinding,
     Known,
     QueryInputs,
 };
@@ -256,8 +256,8 @@ fn test_ground_coll_heterogeneous_types() {
     let schema = prepopulated_schema();
     let known = Known::for_schema(&schema);
     let e = bails(known, &q);
-    match e {
-        Error(ErrorKind::InvalidGroundConstant, _) => {
+    match e.downcast().expect("proper error") {
+        AlgebrizerError::InvalidGroundConstant => {
         },
         _ => {
             panic!();
@@ -271,8 +271,8 @@ fn test_ground_rel_heterogeneous_types() {
     let schema = prepopulated_schema();
     let known = Known::for_schema(&schema);
     let e = bails(known, &q);
-    match e {
-        Error(ErrorKind::InvalidGroundConstant, _) => {
+    match e.downcast().expect("proper error") {
+        AlgebrizerError::InvalidGroundConstant => {
         },
         _ => {
             panic!();
@@ -285,11 +285,10 @@ fn test_ground_tuple_duplicate_vars() {
     let q = r#"[:find ?x :where [?x :foo/age ?v] [(ground [8 10]) [?x ?x]]]"#;
     let schema = prepopulated_schema();
     let known = Known::for_schema(&schema);
-    let e = bails(known, &q);
-    match e {
-        Error(ErrorKind::InvalidBinding(v, e), _) => {
-            assert_eq!(v, PlainSymbol::plain("ground"));
-            assert_eq!(e, BindingError::RepeatedBoundVariable);
+    let e: InvalidBinding = bails(known, &q).downcast().expect("proper error");
+    assert_eq!(e.function, PlainSymbol::plain("ground"));
+    match e.inner.get_context() {
+        &BindingError::RepeatedBoundVariable => {
         },
         _ => {
             panic!();
@@ -302,11 +301,10 @@ fn test_ground_rel_duplicate_vars() {
     let q = r#"[:find ?x :where [?x :foo/age ?v] [(ground [[8 10]]) [[?x ?x]]]]"#;
     let schema = prepopulated_schema();
     let known = Known::for_schema(&schema);
-    let e = bails(known, &q);
-    match e {
-        Error(ErrorKind::InvalidBinding(v, e), _) => {
-            assert_eq!(v, PlainSymbol::plain("ground"));
-            assert_eq!(e, BindingError::RepeatedBoundVariable);
+    let e: InvalidBinding = bails(known, &q).downcast().expect("expected InvalidBinding");
+    assert_eq!(e.function, PlainSymbol::plain("ground"));
+    match e.inner.get_context() {
+        &BindingError::RepeatedBoundVariable => {
         },
         _ => {
             panic!();
@@ -319,9 +317,9 @@ fn test_ground_nonexistent_variable_invalid() {
     let q = r#"[:find ?x ?e :where [?e _ ?x] (not [(ground 17) ?v])]"#;
     let schema = prepopulated_schema();
     let known = Known::for_schema(&schema);
-    let e = bails(known, &q);
+    let e = bails(known, &q).downcast().expect("proper error");
     match e {
-        Error(ErrorKind::UnboundVariable(PlainSymbol(v)), _) => {
+        AlgebrizerError::UnboundVariable(PlainSymbol(v)) => {
             assert_eq!(v, "?v".to_string());
         },
         _ => {
@@ -343,9 +341,9 @@ fn test_unbound_input_variable_invalid() {
 
     let i = QueryInputs::new(types, BTreeMap::default()).expect("valid QueryInputs");
 
-    let e = bails_with_inputs(known, &q, i);
+    let e = bails_with_inputs(known, &q, i).downcast().expect("proper error");
     match e {
-        Error(ErrorKind::UnboundVariable(v), _) => {
+        AlgebrizerError::UnboundVariable(v) => {
             assert_eq!(v.0, "?x");
         },
         _ => {

query-algebrizer/tests/predicate.rs

@@ -31,8 +31,8 @@ use mentat_query::{
 };
 
 use mentat_query_algebrizer::{
+    AlgebrizerError,
     EmptyBecause,
-    ErrorKind,
     Known,
     QueryInputs,
 };
@@ -78,8 +78,8 @@ fn test_instant_predicates_require_instants() {
                     :where
                     [?e :foo/date ?t]
                     [(> ?t "2017-06-16T00:56:41.257Z")]]"#;
-    match bails(known, query).0 {
-        ErrorKind::InvalidArgumentType(op, why, idx) => {
+    match bails(known, query).downcast().expect("proper cause") {
+        AlgebrizerError::InvalidArgumentType(op, why, idx) => {
             assert_eq!(op, PlainSymbol::plain(">"));
             assert_eq!(why, ValueTypeSet::of_numeric_and_instant_types());
             assert_eq!(idx, 1);
@@ -91,8 +91,8 @@ fn test_instant_predicates_require_instants() {
                     :where
                     [?e :foo/date ?t]
                     [(> "2017-06-16T00:56:41.257Z", ?t)]]"#;
-    match bails(known, query).0 {
-        ErrorKind::InvalidArgumentType(op, why, idx) => {
+    match bails(known, query).downcast().expect("proper cause") {
+        AlgebrizerError::InvalidArgumentType(op, why, idx) => {
             assert_eq!(op, PlainSymbol::plain(">"));
             assert_eq!(why, ValueTypeSet::of_numeric_and_instant_types());
             assert_eq!(idx, 0);                      // We get this right.

query-algebrizer/tests/utils/mod.rs

@@ -13,6 +13,9 @@
 // this module will get warnings otherwise).
 #![allow(dead_code)]
 
+extern crate failure;
+use self::failure::Error;
+
 use mentat_core::{
     Attribute,
     Entid,
@@ -26,7 +29,6 @@ use mentat_query::{
 
 use mentat_query_algebrizer::{
     ConjoiningClauses,
-    Error,
     Known,
     QueryInputs,
     algebrize,

query-projector/Cargo.toml

@@ -4,7 +4,8 @@ version = "0.0.1"
 workspace = ".."
 
 [dependencies]
-error-chain = { git = "https://github.com/rnewman/error-chain", branch = "rnewman/sync" }
+failure = "0.1.1"
+failure_derive = "0.1.1"
 indexmap = "1"
 
 [dependencies.rusqlite]

query-projector/src/aggregates.rs

@@ -33,7 +33,7 @@ use mentat_query_sql::{
 };
 
 use errors::{
-    ErrorKind,
+    ProjectorError,
     Result,
 };
 
@@ -79,7 +79,7 @@ impl SimpleAggregationOp {
     pub(crate) fn is_applicable_to_types(&self, possibilities: ValueTypeSet) -> Result<ValueType> {
         use self::SimpleAggregationOp::*;
         if possibilities.is_empty() {
-            bail!(ErrorKind::CannotProjectImpossibleBinding(*self))
+            bail!(ProjectorError::CannotProjectImpossibleBinding(*self))
         }
 
         match self {
@@ -92,7 +92,7 @@ impl SimpleAggregationOp {
                     // The mean of a set of numeric values will always, for our purposes, be a double.
                     Ok(ValueType::Double)
                 } else {
-                    bail!(ErrorKind::CannotApplyAggregateOperationToTypes(*self, possibilities))
+                    bail!(ProjectorError::CannotApplyAggregateOperationToTypes(*self, possibilities))
                 }
             },
             &Sum => {
@@ -104,7 +104,7 @@ impl SimpleAggregationOp {
                         Ok(ValueType::Long)
                     }
                 } else {
-                    bail!(ErrorKind::CannotApplyAggregateOperationToTypes(*self, possibilities))
+                    bail!(ProjectorError::CannotApplyAggregateOperationToTypes(*self, possibilities))
                 }
             },
 
@@ -124,7 +124,7 @@ impl SimpleAggregationOp {
 
                         // These types are unordered.
                         Keyword | Ref | Uuid => {
-                            bail!(ErrorKind::CannotApplyAggregateOperationToTypes(*self, possibilities))
+                            bail!(ProjectorError::CannotApplyAggregateOperationToTypes(*self, possibilities))
                         },
                     }
                 } else {
@@ -139,7 +139,7 @@ impl SimpleAggregationOp {
                             Ok(ValueType::Long)
                         }
                     } else {
-                        bail!(ErrorKind::CannotApplyAggregateOperationToTypes(*self, possibilities))
+                        bail!(ProjectorError::CannotApplyAggregateOperationToTypes(*self, possibilities))
                     }
                 }
             },

query-projector/src/errors.rs

@@ -8,72 +8,58 @@
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
 
-use rusqlite;
+use std; // To refer to std::result::Result.
+
+use failure::{
+    Error,
+};
 
 use mentat_core::{
     ValueTypeSet,
 };
 
-use mentat_db;
-
 use mentat_query::{
     PlainSymbol,
 };
 
-use mentat_query_pull;
-
 use aggregates::{
     SimpleAggregationOp,
 };
 
-error_chain! {
-    types {
-        Error, ErrorKind, ResultExt, Result;
-    }
+#[macro_export]
+macro_rules! bail {
+    ($e:expr) => (
+        return Err($e.into());
+    )
+}
 
-    errors {
+pub type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Debug, Fail)]
+pub enum ProjectorError {
     /// We're just not done yet.  Message that the feature is recognized but not yet
     /// implemented.
-        NotYetImplemented(t: String) {
-            description("not yet implemented")
-            display("not yet implemented: {}", t)
-        }
-        CannotProjectImpossibleBinding(op: SimpleAggregationOp) {
-            description("no possible types for variable in projection list")
-            display("no possible types for value provided to {:?}", op)
-        }
-        CannotApplyAggregateOperationToTypes(op: SimpleAggregationOp, types: ValueTypeSet) {
-            description("cannot apply projection operation to types")
-            display("cannot apply projection operation {:?} to types {:?}", op, types)
-        }
-        InvalidProjection(t: String) {
-            description("invalid projection")
-            display("invalid projection: {}", t)
-        }
-        UnboundVariable(var: PlainSymbol) {
-            description("cannot project unbound variable")
-            display("cannot project unbound variable {:?}", var)
-        }
-        NoTypeAvailableForVariable(var: PlainSymbol) {
-            description("cannot find type for variable")
-            display("cannot find type for variable {:?}", var)
-        }
-        UnexpectedResultsType(actual: &'static str, expected: &'static str) {
-            description("unexpected query results type")
-            display("expected {}, got {}", expected, actual)
-        }
-        AmbiguousAggregates(min_max_count: usize, corresponding_count: usize) {
-            description("ambiguous aggregates")
-            display("min/max expressions: {} (max 1), corresponding: {}", min_max_count, corresponding_count)
-        }
-    }
+    #[fail(display = "not yet implemented: {}", _0)]
+    NotYetImplemented(String),
 
-    foreign_links {
-        Rusqlite(rusqlite::Error);
-    }
+    #[fail(display = "no possible types for value provided to {:?}", _0)]
+    CannotProjectImpossibleBinding(SimpleAggregationOp),
 
-    links {
-        DbError(mentat_db::Error, mentat_db::ErrorKind);
-        PullError(mentat_query_pull::errors::Error, mentat_query_pull::errors::ErrorKind);
-    }
+    #[fail(display = "cannot apply projection operation {:?} to types {:?}", _0, _1)]
+    CannotApplyAggregateOperationToTypes(SimpleAggregationOp, ValueTypeSet),
+
+    #[fail(display = "invalid projection: {}", _0)]
+    InvalidProjection(String),
+
+    #[fail(display = "cannot project unbound variable {:?}", _0)]
+    UnboundVariable(PlainSymbol),
+
+    #[fail(display = "cannot find type for variable {:?}", _0)]
+    NoTypeAvailableForVariable(PlainSymbol),
+
+    #[fail(display = "expected {}, got {}", _0, _1)]
+    UnexpectedResultsType(&'static str, &'static str),
+
+    #[fail(display = "min/max expressions: {} (max 1), corresponding: {}", _0, _1)]
+    AmbiguousAggregates(usize, usize),
 }

query-projector/src/lib.rs

@@ -8,8 +8,10 @@
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
 
+extern crate failure;
+
 #[macro_use]
-extern crate error_chain;
+extern crate failure_derive;
 extern crate indexmap;
 extern crate rusqlite;
 
@@ -67,12 +69,14 @@ use mentat_query_sql::{
     Projection,
 };
 
+#[macro_use]
+pub mod errors;
+
 mod aggregates;
 mod project;
 mod projectors;
 mod pull;
 mod relresult;
-pub mod errors;
 
 pub use aggregates::{
     SimpleAggregationOp,
@@ -109,7 +113,7 @@ pub use relresult::{
 };
 
 use errors::{
-    ErrorKind,
+    ProjectorError,
     Result,
 };
 
@@ -296,35 +300,35 @@ impl QueryResults {
     pub fn into_scalar(self) -> Result<Option<Binding>> {
         match self {
             QueryResults::Scalar(o) => Ok(o),
-            QueryResults::Coll(_) => bail!(ErrorKind::UnexpectedResultsType("coll", "scalar")),
-            QueryResults::Tuple(_) => bail!(ErrorKind::UnexpectedResultsType("tuple", "scalar")),
-            QueryResults::Rel(_) => bail!(ErrorKind::UnexpectedResultsType("rel", "scalar")),
+            QueryResults::Coll(_) => bail!(ProjectorError::UnexpectedResultsType("coll", "scalar")),
+            QueryResults::Tuple(_) => bail!(ProjectorError::UnexpectedResultsType("tuple", "scalar")),
+            QueryResults::Rel(_) => bail!(ProjectorError::UnexpectedResultsType("rel", "scalar")),
         }
     }
 
     pub fn into_coll(self) -> Result<Vec<Binding>> {
         match self {
-            QueryResults::Scalar(_) => bail!(ErrorKind::UnexpectedResultsType("scalar", "coll")),
+            QueryResults::Scalar(_) => bail!(ProjectorError::UnexpectedResultsType("scalar", "coll")),
             QueryResults::Coll(c) => Ok(c),
-            QueryResults::Tuple(_) => bail!(ErrorKind::UnexpectedResultsType("tuple", "coll")),
-            QueryResults::Rel(_) => bail!(ErrorKind::UnexpectedResultsType("rel", "coll")),
+            QueryResults::Tuple(_) => bail!(ProjectorError::UnexpectedResultsType("tuple", "coll")),
+            QueryResults::Rel(_) => bail!(ProjectorError::UnexpectedResultsType("rel", "coll")),
         }
     }
 
     pub fn into_tuple(self) -> Result<Option<Vec<Binding>>> {
         match self {
-            QueryResults::Scalar(_) => bail!(ErrorKind::UnexpectedResultsType("scalar", "tuple")),
-            QueryResults::Coll(_) => bail!(ErrorKind::UnexpectedResultsType("coll", "tuple")),
+            QueryResults::Scalar(_) => bail!(ProjectorError::UnexpectedResultsType("scalar", "tuple")),
+            QueryResults::Coll(_) => bail!(ProjectorError::UnexpectedResultsType("coll", "tuple")),
             QueryResults::Tuple(t) => Ok(t),
-            QueryResults::Rel(_) => bail!(ErrorKind::UnexpectedResultsType("rel", "tuple")),
+            QueryResults::Rel(_) => bail!(ProjectorError::UnexpectedResultsType("rel", "tuple")),
         }
     }
 
     pub fn into_rel(self) -> Result<RelResult<Binding>> {
         match self {
-            QueryResults::Scalar(_) => bail!(ErrorKind::UnexpectedResultsType("scalar", "rel")),
-            QueryResults::Coll(_) => bail!(ErrorKind::UnexpectedResultsType("coll", "rel")),
-            QueryResults::Tuple(_) => bail!(ErrorKind::UnexpectedResultsType("tuple", "rel")),
+            QueryResults::Scalar(_) => bail!(ProjectorError::UnexpectedResultsType("scalar", "rel")),
+            QueryResults::Coll(_) => bail!(ProjectorError::UnexpectedResultsType("coll", "rel")),
+            QueryResults::Tuple(_) => bail!(ProjectorError::UnexpectedResultsType("tuple", "rel")),
             QueryResults::Rel(r) => Ok(r),
         }
     }

query-projector/src/project.rs

@@ -55,7 +55,7 @@ use aggregates::{
 };
 
 use errors::{
-    ErrorKind,
+    ProjectorError,
     Result,
 };
 
@@ -127,14 +127,14 @@ fn candidate_type_column(cc: &ConjoiningClauses, var: &Variable) -> Result<(Colu
           let type_name = VariableColumn::VariableTypeTag(var.clone()).column_name();
           (ColumnOrExpression::Column(alias), type_name)
       })
-      .ok_or_else(|| ErrorKind::UnboundVariable(var.name()).into())
+      .ok_or_else(|| ProjectorError::UnboundVariable(var.name()).into())
 }
 
 fn cc_column(cc: &ConjoiningClauses, var: &Variable) -> Result<QualifiedAlias> {
     cc.column_bindings
       .get(var)
       .and_then(|cols| cols.get(0).cloned())
-      .ok_or_else(|| ErrorKind::UnboundVariable(var.name()).into())
+      .ok_or_else(|| ProjectorError::UnboundVariable(var.name()).into())
 }
 
 fn candidate_column(cc: &ConjoiningClauses, var: &Variable) -> Result<(ColumnOrExpression, Name)> {
@@ -211,18 +211,18 @@ pub(crate) fn project_elements<'a, I: IntoIterator<Item = &'a Element>>(
         match e {
             &Element::Variable(ref var) => {
                 if outer_variables.contains(var) {
-                    bail!(ErrorKind::InvalidProjection(format!("Duplicate variable {} in query.", var)));
+                    bail!(ProjectorError::InvalidProjection(format!("Duplicate variable {} in query.", var)));
                 }
                 if corresponded_variables.contains(var) {
-                    bail!(ErrorKind::InvalidProjection(format!("Can't project both {} and `(the {})` from a query.", var, var)));
+                    bail!(ProjectorError::InvalidProjection(format!("Can't project both {} and `(the {})` from a query.", var, var)));
                 }
             },
             &Element::Corresponding(ref var) => {
                 if outer_variables.contains(var) {
-                    bail!(ErrorKind::InvalidProjection(format!("Can't project both {} and `(the {})` from a query.", var, var)));
+                    bail!(ProjectorError::InvalidProjection(format!("Can't project both {} and `(the {})` from a query.", var, var)));
                 }
                 if corresponded_variables.contains(var) {
-                    bail!(ErrorKind::InvalidProjection(format!("`(the {})` appears twice in query.", var)));
+                    bail!(ProjectorError::InvalidProjection(format!("`(the {})` appears twice in query.", var)));
                 }
             },
             &Element::Aggregate(_) => {
@@ -346,7 +346,7 @@ pub(crate) fn project_elements<'a, I: IntoIterator<Item = &'a Element>>(
                     i += 1;
                 } else {
                     // TODO: complex aggregates.
-                    bail!(ErrorKind::NotYetImplemented("complex aggregates".into()));
+                    bail!(ProjectorError::NotYetImplemented("complex aggregates".into()));
                 }
             },
         }
@@ -355,13 +355,13 @@ pub(crate) fn project_elements<'a, I: IntoIterator<Item = &'a Element>>(
     match (min_max_count, corresponded_variables.len()) {
         (0, 0) | (_, 0) => {},
         (0, _) => {
-            bail!(ErrorKind::InvalidProjection("Warning: used `the` without `min` or `max`.".to_string()));
+            bail!(ProjectorError::InvalidProjection("Warning: used `the` without `min` or `max`.".to_string()));
         },
         (1, _) => {
             // This is the success case!
         },
         (n, c) => {
-            bail!(ErrorKind::AmbiguousAggregates(n, c));
+            bail!(ProjectorError::AmbiguousAggregates(n, c));
         },
     }
 
@@ -465,7 +465,7 @@ pub(crate) fn project_elements<'a, I: IntoIterator<Item = &'a Element>>(
                                     .extracted_types
                                     .get(&var)
                                     .cloned()
-                                    .ok_or_else(|| ErrorKind::NoTypeAvailableForVariable(var.name().clone()))?;
+                                    .ok_or_else(|| ProjectorError::NoTypeAvailableForVariable(var.name().clone()))?;
                 inner_projection.push(ProjectedColumn(ColumnOrExpression::Column(type_col), type_name.clone()));
             }
             if group {

query-projector/src/pull.rs

@@ -30,9 +30,7 @@ use mentat_query_pull::{
     Puller,
 };
 
-use errors::{
-    Result,
-};
+use errors::Result;
 
 use super::{
     Index,

query-projector/tests/aggregates.rs

@@ -99,11 +99,10 @@ fn test_the_without_max_or_min() {
     let projection = query_projection(&schema, &algebrized);
     assert!(projection.is_err());
     use ::mentat_query_projector::errors::{
-        ErrorKind,
-        Error,
+        ProjectorError,
     };
-    match projection {
-        Result::Err(Error(ErrorKind::InvalidProjection(s) , _)) => {
+    match projection.err().expect("expected failure").downcast().expect("expected specific error") {
+        ProjectorError::InvalidProjection(s) => {
                 assert_eq!(s.as_str(), "Warning: used `the` without `min` or `max`.");
             },
         _ => panic!(),

query-pull/Cargo.toml

@@ -4,7 +4,8 @@ version = "0.0.1"
 workspace = ".."
 
 [dependencies]
-error-chain = { git = "https://github.com/rnewman/error-chain", branch = "rnewman/sync" }
+failure = "0.1.1"
+failure_derive = "0.1.1"
 
 [dependencies.rusqlite]
 version = "0.13"

query-pull/src/errors.rs

@@ -8,28 +8,23 @@
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
 
+use std; // To refer to std::result::Result.
+
 use mentat_core::{
     Entid,
 };
 
-error_chain! {
-    types {
-        Error, ErrorKind, ResultExt, Result;
-    }
+use failure::{
+    Error,
+};
 
-    errors {
-        UnnamedAttribute(id: Entid) {
-            description("unnamed attribute")
-            display("attribute {:?} has no name", id)
-        }
+pub type Result<T> = std::result::Result<T, Error>;
 
-        RepeatedDbId {
-            description(":db/id repeated")
-            display(":db/id repeated")
-        }
-    }
+#[derive(Debug, Fail)]
+pub enum PullError {
+    #[fail(display = "attribute {:?} has no name", _0)]
+    UnnamedAttribute(Entid),
 
-    links {
-        DbError(::mentat_db::Error, ::mentat_db::ErrorKind);
-    }
+    #[fail(display = ":db/id repeated")]
+    RepeatedDbId,
 }

query-pull/src/lib.rs

@@ -57,8 +57,10 @@
 ///      [*]))
 ///! ```
 
+extern crate failure;
+
 #[macro_use]
-extern crate error_chain;
+extern crate failure_derive;
 
 extern crate rusqlite;
 
@@ -101,7 +103,7 @@ use mentat_query::{
 pub mod errors;
 
 use errors::{
-    ErrorKind,
+    PullError,
     Result,
 };
 
@@ -163,7 +165,7 @@ impl Puller {
             // In the unlikely event that we have an attribute with no name, we bail.
             schema.get_ident(*i)
                     .map(|ident| ValueRc::new(ident.clone()))
-                    .ok_or_else(|| ErrorKind::UnnamedAttribute(*i))
+                    .ok_or_else(|| PullError::UnnamedAttribute(*i))
         };
 
         let mut names: BTreeMap<Entid, ValueRc<Keyword>> = Default::default();
@@ -192,7 +194,7 @@ impl Puller {
                         &PullConcreteAttribute::Ident(ref i) if i.as_ref() == db_id.as_ref() => {
                             // We only allow :db/id once.
                             if db_id_alias.is_some() {
-                                bail!(ErrorKind::RepeatedDbId);
+                                Err(PullError::RepeatedDbId)?
                             }
                             db_id_alias = Some(alias.unwrap_or_else(|| db_id.to_value_rc()));
                         },

query-sql/src/lib.rs

@@ -42,6 +42,7 @@ use mentat_sql::{
     BuildQueryResult,
     QueryBuilder,
     QueryFragment,
+    SQLError,
     SQLiteQueryBuilder,
     SQLQuery,
 };
@@ -629,7 +630,7 @@ impl QueryFragment for SelectQuery {
 }
 
 impl SelectQuery {
-    pub fn to_sql_query(&self) -> mentat_sql::Result<SQLQuery> {
+    pub fn to_sql_query(&self) -> Result<SQLQuery, SQLError> {
         let mut builder = SQLiteQueryBuilder::new();
         self.push_sql(&mut builder).map(|_| builder.finish())
     }

query-translator/Cargo.toml

@@ -4,7 +4,8 @@ version = "0.0.1"
 workspace = ".."
 
 [dependencies]
-error-chain = { git = "https://github.com/rnewman/error-chain", branch = "rnewman/sync" }
+failure = "0.1.1"
+failure_derive = "0.1.1"
 
 [dependencies.mentat_core]
 path = "../core"

query-translator/src/lib.rs

@@ -8,8 +8,7 @@
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
 
-#[macro_use]
-extern crate error_chain;
+extern crate failure;
 extern crate mentat_core;
 extern crate mentat_query;
 extern crate mentat_query_algebrizer;
@@ -17,6 +16,8 @@ extern crate mentat_query_projector;
 extern crate mentat_query_sql;
 extern crate mentat_sql;
 
+use failure::Error;
+
 mod translate;
 
 pub use mentat_query_sql::{
@@ -29,15 +30,4 @@ pub use translate::{
     query_to_select,
 };
 
-error_chain! {
-    types {
-        Error, ErrorKind, ResultExt, Result;
-    }
-
-    foreign_links {
-    }
-
-    links {
-        ProjectorError(mentat_query_projector::errors::Error, mentat_query_projector::errors::ErrorKind);
-    }
-}
+type Result<T> = std::result::Result<T, Error>;

sql/Cargo.toml

@@ -4,7 +4,8 @@ version = "0.0.1"
 workspace = ".."
 
 [dependencies]
-error-chain = { git = "https://github.com/rnewman/error-chain", branch = "rnewman/sync" }
+failure = "0.1.1"
+failure_derive = "0.1.1"
 ordered-float = "0.5"
 
 [dependencies.rusqlite]

sql/src/lib.rs

@@ -7,9 +7,9 @@
 // under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
+extern crate failure;
 
-#[macro_use]
-extern crate error_chain;
+#[macro_use] extern crate failure_derive;
 extern crate ordered_float;
 extern crate rusqlite;
 
@@ -29,25 +29,16 @@ use mentat_core::{
 
 pub use rusqlite::types::Value;
 
-error_chain! {
-    types {
-        Error, ErrorKind, ResultExt, Result;
-    }
+#[derive(Debug, Fail)]
+pub enum SQLError {
+    #[fail(display = "invalid parameter name: {}", _0)]
+    InvalidParameterName(String),
 
-    errors {
-        InvalidParameterName(name: String) {
-            description("invalid parameter name")
-            display("invalid parameter name: '{}'", name)
-        }
-
-        BindParamCouldBeGenerated(name: String) {
-            description("parameter name could be generated")
-            display("parameter name could be generated: '{}'", name)
-        }
-    }
+    #[fail(display = "parameter name could be generated: '{}'", _0)]
+    BindParamCouldBeGenerated(String)
 }
 
-pub type BuildQueryResult = Result<()>;
+pub type BuildQueryResult = Result<(), SQLError>;
 
 /// We want to accumulate values that will later be substituted into a SQL statement execution.
 /// This struct encapsulates the generated string and the _initial_ argument list.
@@ -213,12 +204,12 @@ impl QueryBuilder for SQLiteQueryBuilder {
         // Do some validation first.
         // This is not free, but it's probably worth it for now.
         if !name.chars().all(|c| char::is_alphanumeric(c) || c == '_') {
-            bail!(ErrorKind::InvalidParameterName(name.to_string()));
+            return Err(SQLError::InvalidParameterName(name.to_string()))
         }
 
         if name.starts_with(self.arg_prefix.as_str()) &&
            name.chars().skip(self.arg_prefix.len()).all(char::is_numeric) {
-               bail!(ErrorKind::BindParamCouldBeGenerated(name.to_string()));
+               return Err(SQLError::BindParamCouldBeGenerated(name.to_string()))
         }
 
         self.push_sql("$");

src/conn.rs

@@ -93,7 +93,10 @@ use entity_builder::{
     TermBuilder,
 };
 
-use errors::*;
+use errors::{
+    Result,
+    MentatError,
+};
 
 use query::{
     Known,
@@ -474,7 +477,7 @@ impl<'a, 'c> InProgress<'a, 'c> {
             // Retrying is tracked by https://github.com/mozilla/mentat/issues/357.
             // This should not occur -- an attempt to take a competing IMMEDIATE transaction
             // will fail with `SQLITE_BUSY`, causing this function to abort.
-            bail!("Lost the transact() race!");
+            bail!(MentatError::UnexpectedLostTransactRace);
         }
 
         // Commit the SQLite transaction while we hold the mutex.
@@ -506,7 +509,7 @@ impl<'a, 'c> InProgress<'a, 'c> {
                  cache_action: CacheAction) -> Result<()> {
         let attribute_entid: Entid = self.schema
                                          .attribute_for_ident(&attribute)
-                                         .ok_or_else(|| ErrorKind::UnknownAttribute(attribute.to_string()))?.1.into();
+                                         .ok_or_else(|| MentatError::UnknownAttribute(attribute.to_string()))?.1.into();
 
         match cache_action {
             CacheAction::Register => {
@@ -579,17 +582,16 @@ impl Conn {
     /// Prepare the provided SQLite handle for use as a Mentat store. Creates tables but
     /// _does not_ write the bootstrap schema. This constructor should only be used by
     /// consumers that expect to populate raw transaction data themselves.
+
     pub(crate) fn empty(sqlite: &mut rusqlite::Connection) -> Result<Conn> {
-        let (tx, db) = db::create_empty_current_version(sqlite)
-            .chain_err(|| "Unable to initialize Mentat store")?;
+        let (tx, db) = db::create_empty_current_version(sqlite)?;
         tx.commit()?;
         Ok(Conn::new(db.partition_map, db.schema))
     }
 
 
     pub fn connect(sqlite: &mut rusqlite::Connection) -> Result<Conn> {
-        let db = db::ensure_current_version(sqlite)
-            .chain_err(|| "Unable to initialize Mentat store")?;
+        let db = db::ensure_current_version(sqlite)?;
         Ok(Conn::new(db.partition_map, db.schema))
     }
 
@@ -801,7 +803,7 @@ impl Conn {
         {
             attribute_entid = metadata.schema
                                       .attribute_for_ident(&attribute)
-                                      .ok_or_else(|| ErrorKind::UnknownAttribute(attribute.to_string()))?.1.into();
+                                      .ok_or_else(|| MentatError::UnknownAttribute(attribute.to_string()))?.1.into();
         }
 
         let cache = &mut metadata.attribute_cache;
@@ -869,11 +871,11 @@ mod tests {
                        .partition_map[":db.part/user"].index;
         let t = format!("[[:db/add {} :db.schema/attribute \"tempid\"]]", next + 1);
 
-        match conn.transact(&mut sqlite, t.as_str()).unwrap_err() {
-            Error(ErrorKind::DbError(::mentat_db::errors::ErrorKind::UnrecognizedEntid(e)), _) => {
+        match conn.transact(&mut sqlite, t.as_str()).expect_err("expected transact error").downcast() {
+            Ok(::mentat_db::DbError::UnrecognizedEntid(e)) => {
                 assert_eq!(e, next + 1);
             },
-            x => panic!("expected transact error, got {:?}", x),
+            x => panic!("expected db error, got {:?}", x),
         }
 
         // Transact two more tempids.
@@ -896,12 +898,12 @@ mod tests {
         // we should reject this, because the first ID was provided by the user!
         let t = format!("[[:db/add {} :db.schema/attribute \"tempid\"]]", next);
 
-        match conn.transact(&mut sqlite, t.as_str()).unwrap_err() {
-            Error(ErrorKind::DbError(::mentat_db::errors::ErrorKind::UnrecognizedEntid(e)), _) => {
+        match conn.transact(&mut sqlite, t.as_str()).expect_err("expected transact error").downcast() {
+            Ok(::mentat_db::DbError::UnrecognizedEntid(e)) => {
                 // All this, despite this being the ID we were about to allocate!
                 assert_eq!(e, next);
             },
-            x => panic!("expected transact error, got {:?}", x),
+            x => panic!("expected db error, got {:?}", x),
         }
 
         // And if we subsequently transact in a way that allocates one ID, we _will_ use that one.
@@ -1057,9 +1059,9 @@ mod tests {
 
         // Bad EDN: missing closing ']'.
         let report = conn.transact(&mut sqlite, "[[:db/add \"t\" :db/ident :a/keyword]");
-        match report.unwrap_err() {
-            Error(ErrorKind::EdnParseError(_), _) => { },
-            x => panic!("expected EDN parse error, got {:?}", x),
+        match report.expect_err("expected transact to fail for bad edn").downcast() {
+            Ok(edn::ParseError { .. }) => { },
+            Err(x) => panic!("expected EDN parse error, got {:?}", x),
         }
 
         // Good EDN.
@@ -1068,9 +1070,9 @@ mod tests {
 
         // Bad transaction data: missing leading :db/add.
         let report = conn.transact(&mut sqlite, "[[\"t\" :db/ident :b/keyword]]");
-        match report.unwrap_err() {
-            Error(ErrorKind::EdnParseError(_), _) => { },
-            x => panic!("expected EDN parse error, got {:?}", x),
+        match report.expect_err("expected transact error").downcast() {
+            Ok(edn::ParseError { .. }) => { },
+            Err(x) => panic!("expected EDN parse error, got {:?}", x),
         }
 
         // Good transaction data.
@@ -1080,8 +1082,8 @@ mod tests {
         // Bad transaction based on state of store: conflicting upsert.
         let report = conn.transact(&mut sqlite, "[[:db/add \"u\" :db/ident :a/keyword]
                                                   [:db/add \"u\" :db/ident :b/keyword]]");
-        match report.unwrap_err() {
-            Error(ErrorKind::DbError(::mentat_db::errors::ErrorKind::SchemaConstraintViolation(_)), _) => { },
+        match report.expect_err("expected transact error").downcast() {
+            Ok(::mentat_db::DbError::SchemaConstraintViolation(_)) => { },
             x => panic!("expected schema constraint violation, got {:?}", x),
         }
     }
@@ -1099,8 +1101,8 @@ mod tests {
         let kw = kw!(:foo/bat);
         let schema = conn.current_schema();
         let res = conn.cache(&mut sqlite, &schema, &kw, CacheDirection::Forward, CacheAction::Register);
-        match res.unwrap_err() {
-            Error(ErrorKind::UnknownAttribute(msg), _) => assert_eq!(msg, ":foo/bat"),
+        match res.expect_err("expected cache to fail").downcast() {
+            Ok(MentatError::UnknownAttribute(msg)) => assert_eq!(msg, ":foo/bat"),
             x => panic!("expected UnknownAttribute error, got {:?}", x),
         }
     }

src/entity_builder.rs

@@ -85,7 +85,7 @@ use conn::{
 };
 
 use errors::{
-    ErrorKind,
+    MentatError,
     Result,
 };
 
@@ -277,12 +277,12 @@ impl<'a, 'c> InProgressBuilder<'a, 'c> {
                 let provided = tv.value_type();
                 let expected = attr.value_type;
                 if provided != expected {
-                    bail!(ErrorKind::ValueTypeMismatch(provided, expected));
+                    bail!(MentatError::ValueTypeMismatch(provided, expected));
                 }
             }
             attribute = aa;
         } else {
-            bail!(ErrorKind::UnknownAttribute(a.to_string()));
+            bail!(MentatError::UnknownAttribute(a.to_string()));
         }
         Ok((attribute, v))
     }
@@ -380,15 +380,8 @@ impl FromThing<KnownEntid> for TypedValueOr<TempIdHandle> {
 mod testing {
     extern crate mentat_db;
 
-    use errors::{
-        Error,
-        ErrorKind,
-    };
-
     // For matching inside a test.
-    use mentat_db::ErrorKind::{
-        UnrecognizedEntid,
-    };
+    use mentat_db::DbError;
 
     use ::{
         Conn,
@@ -429,7 +422,7 @@ mod testing {
         let mut in_progress = conn.begin_transaction(&mut sqlite).expect("begun successfully");
 
         // This should fail: unrecognized entid.
-        if let Err(Error(ErrorKind::DbError(UnrecognizedEntid(e)), _)) = in_progress.transact_terms(terms, tempids) {
+        if let Ok(DbError::UnrecognizedEntid(e)) = in_progress.transact_terms(terms, tempids).expect_err("expected transact to fail").downcast() {
             assert_eq!(e, 999);
         } else {
             panic!("Should have rejected the entid.");

src/errors.rs

@@ -10,102 +10,63 @@
 
 #![allow(dead_code)]
 
-use rusqlite;
-
-use uuid;
+use std; // To refer to std::result::Result.
 
 use std::collections::BTreeSet;
 
-use edn;
+use failure::Error;
+
 use mentat_core::{
     Attribute,
     ValueType,
 };
-use mentat_db;
+
 use mentat_query;
-use mentat_query_algebrizer;
-use mentat_query_projector;
-use mentat_query_pull;
-use mentat_query_translator;
-use mentat_sql;
-use mentat_tolstoy;
 
-error_chain! {
-    types {
-        Error, ErrorKind, ResultExt, Result;
-    }
+pub type Result<T> = std::result::Result<T, Error>;
 
-    foreign_links {
-        EdnParseError(edn::ParseError);
-        Rusqlite(rusqlite::Error);
-        UuidParseError(uuid::ParseError);
-        IoError(::std::io::Error);
-    }
-
-    links {
-        DbError(mentat_db::Error, mentat_db::ErrorKind);
-        QueryError(mentat_query_algebrizer::Error, mentat_query_algebrizer::ErrorKind);   // Let's not leak the term 'algebrizer'.
-        ProjectorError(mentat_query_projector::errors::Error, mentat_query_projector::errors::ErrorKind);
-        PullError(mentat_query_pull::errors::Error, mentat_query_pull::errors::ErrorKind);
-        TranslatorError(mentat_query_translator::Error, mentat_query_translator::ErrorKind);
-        SqlError(mentat_sql::Error, mentat_sql::ErrorKind);
-        SyncError(mentat_tolstoy::Error, mentat_tolstoy::ErrorKind);
-    }
-
-    errors {
-        PathAlreadyExists(path: String) {
-            description("path already exists")
-            display("path {} already exists", path)
-        }
-
-        UnboundVariables(names: BTreeSet<String>) {
-            description("unbound variables at query execution time")
-            display("variables {:?} unbound at query execution time", names)
-        }
-
-        InvalidArgumentName(name: String) {
-            description("invalid argument name")
-            display("invalid argument name: '{}'", name)
-        }
-
-        UnknownAttribute(name: String) {
-            description("unknown attribute")
-            display("unknown attribute: '{}'", name)
-        }
-
-        InvalidVocabularyVersion {
-            description("invalid vocabulary version")
-            display("invalid vocabulary version")
-        }
-
-        ConflictingAttributeDefinitions(vocabulary: String, version: ::vocabulary::Version, attribute: String, current: Attribute, requested: Attribute) {
-            description("conflicting attribute definitions")
-            display("vocabulary {}/{} already has attribute {}, and the requested definition differs", vocabulary, version, attribute)
-        }
-
-        ExistingVocabularyTooNew(name: String, existing: ::vocabulary::Version, ours: ::vocabulary::Version) {
-            description("existing vocabulary too new")
-            display("existing vocabulary too new: wanted {}, got {}", ours, existing)
-        }
-
-        UnexpectedCoreSchema(version: Option<::vocabulary::Version>) {
-            description("unexpected core schema version")
-            display("core schema: wanted {}, got {:?}", mentat_db::CORE_SCHEMA_VERSION, version)
-        }
-
-        MissingCoreVocabulary(kw: mentat_query::Keyword) {
-            description("missing core vocabulary")
-            display("missing core attribute {}", kw)
-        }
-
-        PreparedQuerySchemaMismatch {
-            description("schema changed since query was prepared")
-            display("schema changed since query was prepared")
-        }
-
-        ValueTypeMismatch(provided: ValueType, expected: ValueType) {
-            description("provided value doesn't match value type")
-            display("provided value of type {} doesn't match attribute value type {}", provided, expected)
-        }
-    }
+#[macro_export]
+macro_rules! bail {
+    ($e:expr) => (
+        return Err($e.into());
+    )
+}
+
+#[derive(Debug, Fail)]
+pub enum MentatError {
+    #[fail(display = "path {} already exists", _0)]
+    PathAlreadyExists(String),
+
+    #[fail(display = "variables {:?} unbound at query execution time", _0)]
+    UnboundVariables(BTreeSet<String>),
+
+    #[fail(display = "invalid argument name: '{}'", _0)]
+    InvalidArgumentName(String),
+
+    #[fail(display = "unknown attribute: '{}'", _0)]
+    UnknownAttribute(String),
+
+    #[fail(display = "invalid vocabulary version")]
+    InvalidVocabularyVersion,
+
+    #[fail(display = "vocabulary {}/{} already has attribute {}, and the requested definition differs", _0, _1, _2)]
+    ConflictingAttributeDefinitions(String, ::vocabulary::Version, String, Attribute, Attribute),
+
+    #[fail(display = "existing vocabulary {} too new: wanted {}, got {}", _0, _1, _2)]
+    ExistingVocabularyTooNew(String, ::vocabulary::Version, ::vocabulary::Version),
+
+    #[fail(display = "core schema: wanted {}, got {:?}", _0, _1)]
+    UnexpectedCoreSchema(::vocabulary::Version, Option<::vocabulary::Version>),
+
+    #[fail(display = "Lost the transact() race!")]
+    UnexpectedLostTransactRace,
+
+    #[fail(display = "missing core attribute {}", _0)]
+    MissingCoreVocabulary(mentat_query::Keyword),
+
+    #[fail(display = "schema changed since query was prepared")]
+    PreparedQuerySchemaMismatch,
+
+    #[fail(display = "provided value of type {} doesn't match attribute value type {}", _0, _1)]
+    ValueTypeMismatch(ValueType, ValueType),
 }

src/lib.rs

@@ -11,7 +11,8 @@
 #![recursion_limit="128"]
 
 #[macro_use]
-extern crate error_chain;
+extern crate failure_derive;
+extern crate failure;
 
 #[macro_use]
 extern crate lazy_static;
@@ -101,9 +102,10 @@ macro_rules! kw {
     };
 }
 
+#[macro_use]
+pub mod errors;
 pub mod conn;
 pub mod entity_builder;
-pub mod errors;
 pub mod ident;
 pub mod query;
 pub mod query_builder;

src/query.rs

@@ -74,7 +74,7 @@ pub use mentat_query_projector::{
 };
 
 use errors::{
-    ErrorKind,
+    MentatError,
     Result,
 };
 
@@ -178,7 +178,7 @@ fn algebrize_query<T>
     // If they aren't, the user has made an error -- perhaps writing the wrong variable in `:in`, or
     // not binding in the `QueryInput`.
     if !unbound.is_empty() {
-        bail!(ErrorKind::UnboundVariables(unbound.into_iter().map(|v| v.to_string()).collect()));
+        bail!(MentatError::UnboundVariables(unbound.into_iter().map(|v| v.to_string()).collect()));
     }
     Ok(algebrized)
 }
@@ -211,7 +211,7 @@ fn fetch_values<'sqlite>
 
 fn lookup_attribute(schema: &Schema, attribute: &Keyword) -> Result<KnownEntid> {
     schema.get_entid(attribute)
-          .ok_or_else(|| ErrorKind::UnknownAttribute(attribute.name().into()).into())
+          .ok_or_else(|| MentatError::UnknownAttribute(attribute.name().into()).into())
 }
 
 /// Return a single value for the provided entity and attribute.
@@ -398,7 +398,7 @@ pub fn q_prepare<'sqlite, 'schema, 'cache, 'query, T>
     if !unbound.is_empty() {
         // TODO: Allow binding variables at execution time, not just
         // preparation time.
-        bail!(ErrorKind::UnboundVariables(unbound.into_iter().map(|v| v.to_string()).collect()));
+        bail!(MentatError::UnboundVariables(unbound.into_iter().map(|v| v.to_string()).collect()));
     }
 
     if algebrized.is_known_empty() {

src/query_builder.rs

@@ -34,7 +34,7 @@ use ::{
 };
 
 use errors::{
-    ErrorKind,
+    MentatError,
     Result,
 };
 
@@ -56,7 +56,7 @@ impl<'a> QueryBuilder<'a> {
     }
 
     pub fn bind_ref_from_kw(&mut self, var: &str, value: Keyword) -> Result<&mut Self> {
-        let entid = self.store.conn().current_schema().get_entid(&value).ok_or(ErrorKind::UnknownAttribute(value.to_string()))?;
+        let entid = self.store.conn().current_schema().get_entid(&value).ok_or(MentatError::UnknownAttribute(value.to_string()))?;
         self.values.insert(Variable::from_valid_name(var), TypedValue::Ref(entid.into()));
         Ok(self)
     }

src/store.rs

@@ -84,7 +84,7 @@ impl Store {
     pub fn open_empty(path: &str) -> Result<Store> {
         if !path.is_empty() {
             if Path::new(path).exists() {
-                bail!(ErrorKind::PathAlreadyExists(path.to_string()));
+                bail!(MentatError::PathAlreadyExists(path.to_string()));
             }
         }
 
@@ -124,7 +124,7 @@ impl Store {
     pub fn open_empty_with_key(path: &str, encryption_key: &str) -> Result<Store> {
         if !path.is_empty() {
             if Path::new(path).exists() {
-                bail!(ErrorKind::PathAlreadyExists(path.to_string()));
+                bail!(MentatError::PathAlreadyExists(path.to_string()));
             }
         }
 

src/vocabulary.rs

@@ -121,7 +121,7 @@ use ::conn::{
 };
 
 use ::errors::{
-    ErrorKind,
+    MentatError,
     Result,
 };
 
@@ -375,17 +375,17 @@ trait HasCoreSchema {
 impl<T> HasCoreSchema for T where T: HasSchema {
     fn core_type(&self, t: ValueType) -> Result<KnownEntid> {
         self.entid_for_type(t)
-            .ok_or_else(|| ErrorKind::MissingCoreVocabulary(DB_SCHEMA_VERSION.clone()).into())
+            .ok_or_else(|| MentatError::MissingCoreVocabulary(DB_SCHEMA_VERSION.clone()).into())
     }
 
     fn core_entid(&self, ident: &Keyword) -> Result<KnownEntid> {
         self.get_entid(ident)
-            .ok_or_else(|| ErrorKind::MissingCoreVocabulary(DB_SCHEMA_VERSION.clone()).into())
+            .ok_or_else(|| MentatError::MissingCoreVocabulary(DB_SCHEMA_VERSION.clone()).into())
     }
 
     fn core_attribute(&self, ident: &Keyword) -> Result<KnownEntid> {
         self.attribute_for_ident(ident)
-            .ok_or_else(|| ErrorKind::MissingCoreVocabulary(DB_SCHEMA_VERSION.clone()).into())
+            .ok_or_else(|| MentatError::MissingCoreVocabulary(DB_SCHEMA_VERSION.clone()).into())
             .map(|(_, e)| e)
     }
 }
@@ -568,7 +568,7 @@ pub trait VersionedStore: HasVocabularies + HasSchema {
                                 // We have two vocabularies with the same name, same version, and
                                 // different definitions for an attribute. That's a coding error.
                                 // We can't accept this vocabulary.
-                                bail!(ErrorKind::ConflictingAttributeDefinitions(
+                                bail!(MentatError::ConflictingAttributeDefinitions(
                                           definition.name.to_string(),
                                           definition.version,
                                           pair.0.to_string(),
@@ -615,13 +615,13 @@ pub trait VersionedStore: HasVocabularies + HasSchema {
     fn verify_core_schema(&self) -> Result<()> {
         if let Some(core) = self.read_vocabulary_named(&DB_SCHEMA_CORE)? {
             if core.version != CORE_SCHEMA_VERSION {
-                bail!(ErrorKind::UnexpectedCoreSchema(Some(core.version)));
+                bail!(MentatError::UnexpectedCoreSchema(CORE_SCHEMA_VERSION, Some(core.version)));
             }
 
             // TODO: check things other than the version.
         } else {
             // This would be seriously messed up.
-            bail!(ErrorKind::UnexpectedCoreSchema(None));
+            bail!(MentatError::UnexpectedCoreSchema(CORE_SCHEMA_VERSION, None));
         }
         Ok(())
     }
@@ -682,7 +682,7 @@ impl<'a, 'c> VersionedStore for InProgress<'a, 'c> {
             VocabularyCheck::NotPresent => self.install_vocabulary(definition),
             VocabularyCheck::PresentButNeedsUpdate { older_version } => self.upgrade_vocabulary(definition, older_version),
             VocabularyCheck::PresentButMissingAttributes { attributes } => self.install_attributes_for(definition, attributes),
-            VocabularyCheck::PresentButTooNew { newer_version } => Err(ErrorKind::ExistingVocabularyTooNew(definition.name.to_string(), newer_version.version, definition.version).into()),
+            VocabularyCheck::PresentButTooNew { newer_version } => Err(MentatError::ExistingVocabularyTooNew(definition.name.to_string(), newer_version.version, definition.version).into()),
         }
     }
 
@@ -701,7 +701,7 @@ impl<'a, 'c> VersionedStore for InProgress<'a, 'c> {
                     out.insert(definition.name.clone(), VocabularyOutcome::Existed);
                 },
                 VocabularyCheck::PresentButTooNew { newer_version } => {
-                    bail!(ErrorKind::ExistingVocabularyTooNew(definition.name.to_string(), newer_version.version, definition.version));
+                    bail!(MentatError::ExistingVocabularyTooNew(definition.name.to_string(), newer_version.version, definition.version));
                 },
 
                 c @ VocabularyCheck::NotPresent |
@@ -868,7 +868,7 @@ impl<T> HasVocabularies for T where T: HasSchema + Queryable {
                             attributes: attributes,
                         }))
                     },
-                Some(_) => bail!(ErrorKind::InvalidVocabularyVersion),
+                Some(_) => bail!(MentatError::InvalidVocabularyVersion),
             }
         } else {
             Ok(None)

tests/query.rs

@@ -61,8 +61,7 @@ use mentat::query::q_uncached;
 use mentat::conn::Conn;
 
 use mentat::errors::{
-    Error,
-    ErrorKind,
+    MentatError,
 };
 
 #[test]
@@ -234,11 +233,11 @@ fn test_unbound_inputs() {
     let results = q_uncached(&c, &db.schema,
                              "[:find ?i . :in ?e :where [?e :db/ident ?i]]", inputs);
 
-    match results {
-        Result::Err(Error(ErrorKind::UnboundVariables(vars), _)) => {
+    match results.expect_err("expected unbound variables").downcast().expect("expected specific error") {
+        MentatError::UnboundVariables(vars) => {
             assert_eq!(vars, vec!["?e".to_string()].into_iter().collect());
         },
-        _ => panic!("Expected unbound variables."),
+        _ => panic!("Expected UnboundVariables variant."),
     }
 }
 
@@ -412,8 +411,8 @@ fn test_fulltext() {
                     [?a :foo/term ?term]
                     ]"#;
     let r = conn.q_once(&mut c, query, None);
-    match r {
-        Err(Error(ErrorKind::QueryError(mentat_query_algebrizer::ErrorKind::InvalidArgument(PlainSymbol(s), ty, i)), _)) => {
+    match r.expect_err("expected query to fail").downcast() {
+        Ok(mentat_query_algebrizer::AlgebrizerError::InvalidArgument(PlainSymbol(s), ty, i)) => {
             assert_eq!(s, "fulltext");
             assert_eq!(ty, "string");
             assert_eq!(i, 2);
@@ -427,8 +426,8 @@ fn test_fulltext() {
                     [?a :foo/term ?term]
                     [(fulltext $ :foo/fts ?a) [[?x ?val]]]]"#;
     let r = conn.q_once(&mut c, query, None);
-    match r {
-        Err(Error(ErrorKind::QueryError(mentat_query_algebrizer::ErrorKind::InvalidArgument(PlainSymbol(s), ty, i)), _)) => {
+    match r.expect_err("expected query to fail").downcast() {
+        Ok(mentat_query_algebrizer::AlgebrizerError::InvalidArgument(PlainSymbol(s), ty, i)) => {
             assert_eq!(s, "fulltext");
             assert_eq!(ty, "string");
             assert_eq!(i, 2);
@@ -583,42 +582,25 @@ fn test_aggregates_type_handling() {
     // No type limits => can't do it.
     let r = store.q_once(r#"[:find (sum ?v) . :where [_ _ ?v]]"#, None);
     let all_types = ValueTypeSet::any();
-    match r {
-        Result::Err(
-            Error(
-                ErrorKind::TranslatorError(
-                    ::mentat_query_translator::ErrorKind::ProjectorError(
-                        ::mentat_query_projector::errors::ErrorKind::CannotApplyAggregateOperationToTypes(
-                            SimpleAggregationOp::Sum,
-                            types
-                        ),
-                    )
-                ),
-                _)) => {
+    match r.expect_err("expected query to fail").downcast() {
+        Ok(::mentat_query_projector::errors::ProjectorError::CannotApplyAggregateOperationToTypes(
+            SimpleAggregationOp::Sum, types)) => {
                 assert_eq!(types, all_types);
         },
-        r => panic!("Unexpected: {:?}", r),
+        e => panic!("Unexpected error type {:?}", e),
     }
 
     // You can't sum instants.
     let r = store.q_once(r#"[:find (sum ?v) .
                              :where [_ _ ?v] [(type ?v :db.type/instant)]]"#,
                          None);
-    match r {
-        Result::Err(
-            Error(
-                ErrorKind::TranslatorError(
-                    ::mentat_query_translator::ErrorKind::ProjectorError(
-                        ::mentat_query_projector::errors::ErrorKind::CannotApplyAggregateOperationToTypes(
+    match r.expect_err("expected query to fail").downcast() {
+        Ok(::mentat_query_projector::errors::ProjectorError::CannotApplyAggregateOperationToTypes(
             SimpleAggregationOp::Sum,
-                            types
-                        ),
-                    )
-                ),
-                _)) => {
+            types)) => {
                 assert_eq!(types, ValueTypeSet::of_one(ValueType::Instant));
         },
-        r => panic!("Unexpected: {:?}", r),
+        e => panic!("Unexpected error type {:?}", e),
     }
 
     // But you can count them.
@@ -1354,19 +1336,13 @@ fn test_aggregation_implicit_grouping() {
                                [?person :foo/play ?game]
                                [?person :foo/is-vegetarian true]
                                [?person :foo/name ?name]]"#, None);
-    match res {
-        Result::Err(
-            Error(
-                ErrorKind::TranslatorError(
-                    ::mentat_query_translator::ErrorKind::ProjectorError(
-                        ::mentat_query_projector::errors::ErrorKind::AmbiguousAggregates(mmc, cc)
-                    )
-            ), _)) => {
+    match res.expect_err("expected query to fail").downcast() {
+        Ok(::mentat_query_projector::errors::ProjectorError::AmbiguousAggregates(mmc, cc)) => {
             assert_eq!(mmc, 2);
             assert_eq!(cc, 1);
         },
-        r => {
-            panic!("Unexpected result {:?}.", r);
+        e => {
+            panic!("Unexpected error type {:?}.", e);
         },
     }
 

tests/vocabulary.rs

@@ -59,10 +59,7 @@ use mentat::entity_builder::{
     TermBuilder,
 };
 
-use mentat::errors::{
-    Error,
-    ErrorKind,
-};
+use mentat::errors::MentatError;
 
 lazy_static! {
     static ref FOO_NAME: Keyword = {
@@ -289,8 +286,8 @@ fn test_add_vocab() {
     // Scoped borrow of `conn`.
     {
         let mut in_progress = conn.begin_transaction(&mut sqlite).expect("begun successfully");
-        match in_progress.ensure_vocabulary(&foo_v1_malformed) {
-            Result::Err(Error(ErrorKind::ConflictingAttributeDefinitions(vocab, version, attr, theirs, ours), _)) => {
+        match in_progress.ensure_vocabulary(&foo_v1_malformed).expect_err("expected vocabulary to fail").downcast() {
+            Ok(MentatError::ConflictingAttributeDefinitions(vocab, version, attr, theirs, ours)) => {
                 assert_eq!(vocab.as_str(), ":org.mozilla/foo");
                 assert_eq!(attr.as_str(), ":foo/baz");
                 assert_eq!(version, 1);

tolstoy/Cargo.toml

@@ -5,6 +5,8 @@ workspace = ".."
 authors = ["Grisha Kruglov <gkruglov@mozilla.com>"]
 
 [dependencies]
+failure = "0.1.1"
+failure_derive = "0.1.1"
 futures = "0.1"
 hyper = "0.11"
 tokio-core = "0.1"
@@ -15,8 +17,6 @@ serde_derive = "1.0"
 lazy_static = "0.2"
 uuid = { version = "0.5", features = ["v4", "serde"] }
 
-error-chain = { git = "https://github.com/rnewman/error-chain", branch = "rnewman/sync" }
-
 [dependencies.mentat_core]
 path = "../core"
 

tolstoy/src/errors.rs

@@ -10,63 +10,34 @@
 
 #![allow(dead_code)]
 
-use std;
-use hyper;
-use rusqlite;
-use uuid;
-use mentat_db;
-use serde_cbor;
-use serde_json;
+use failure::Error;
 
-error_chain! {
-    types {
-        Error, ErrorKind, ResultExt, Result;
-    }
-
-    foreign_links {
-        IOError(std::io::Error);
-        HttpError(hyper::Error);
-        HyperUriError(hyper::error::UriError);
-        SqlError(rusqlite::Error);
-        UuidParseError(uuid::ParseError);
-        Utf8Error(std::str::Utf8Error);
-        JsonError(serde_json::Error);
-        CborError(serde_cbor::error::Error);
-    }
-
-    links {
-        DbError(mentat_db::Error, mentat_db::ErrorKind);
-    }
-
-    errors {
-        TxIncorrectlyMapped(n: usize) {
-            description("encountered more than one uuid mapping for tx")
-            display("expected one, found {} uuid mappings for tx", n)
-        }
-
-        UnexpectedState(t: String) {
-            description("encountered unexpected state")
-            display("encountered unexpected state: {}", t)
-        }
-
-        NotYetImplemented(t: String) {
-            description("not yet implemented")
-            display("not yet implemented: {}", t)
-        }
-
-        DuplicateMetadata(k: String) {
-            description("encountered more than one metadata value for key")
-            display("encountered more than one metadata value for key: {}", k)
-        }
-
-        TxProcessorUnfinished {
-            description("Tx processor couldn't finish")
-            display("Tx processor couldn't finish")
-        }
-
-        BadServerResponse(s: String) {
-            description("Received bad response from the server")
-            display("Received bad response from the server: {}", s)
-        }
-    }
+#[macro_export]
+macro_rules! bail {
+    ($e:expr) => (
+        return Err($e.into());
+    )
+}
+
+pub type Result<T> = ::std::result::Result<T, Error>;
+
+#[derive(Debug, Fail)]
+pub enum TolstoyError {
+    #[fail(display = "Received bad response from the server: {}", _0)]
+    BadServerResponse(String),
+
+    #[fail(display = "encountered more than one metadata value for key: {}", _0)]
+    DuplicateMetadata(String),
+
+    #[fail(display = "transaction processor didn't say it was done")]
+    TxProcessorUnfinished,
+
+    #[fail(display = "expected one, found {} uuid mappings for tx", _0)]
+    TxIncorrectlyMapped(usize),
+
+    #[fail(display = "encountered unexpected state: {}", _0)]
+    UnexpectedState(String),
+
+    #[fail(display = "not yet implemented: {}", _0)]
+    NotYetImplemented(String),
 }

tolstoy/src/lib.rs

@@ -8,11 +8,9 @@
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
 
-// For error_chain:
-#![recursion_limit="128"]
-
+extern crate failure;
 #[macro_use]
-extern crate error_chain;
+extern crate failure_derive;
 
 #[macro_use]
 extern crate lazy_static;
@@ -33,16 +31,15 @@ extern crate mentat_core;
 extern crate rusqlite;
 extern crate uuid;
 
+#[macro_use]
+pub mod errors;
 pub mod schema;
 pub mod metadata;
 pub mod tx_processor;
-pub mod errors;
 pub mod syncer;
 pub mod tx_mapper;
 pub use syncer::Syncer;
 pub use errors::{
-    Error,
-    ErrorKind,
+    TolstoyError,
     Result,
-    ResultExt,
 };

tolstoy/src/metadata.rs

@@ -15,7 +15,7 @@ use uuid::Uuid;
 
 use schema;
 use errors::{
-    ErrorKind,
+    TolstoyError,
     Result,
 };
 
@@ -42,7 +42,7 @@ impl HeadTrackable for SyncMetadataClient {
         let updated = tx.execute("UPDATE tolstoy_metadata SET value = ? WHERE key = ?",
             &[&uuid_bytes, &schema::REMOTE_HEAD_KEY])?;
         if updated != 1 {
-            bail!(ErrorKind::DuplicateMetadata(schema::REMOTE_HEAD_KEY.into()));
+            bail!(TolstoyError::DuplicateMetadata(schema::REMOTE_HEAD_KEY.into()));
         }
         Ok(())
     }

tolstoy/src/syncer.rs

@@ -31,7 +31,7 @@ use metadata::HeadTrackable;
 use schema::ensure_current_version;
 
 use errors::{
-    ErrorKind,
+    TolstoyError,
     Result,
 };
 
@@ -179,7 +179,7 @@ impl Syncer {
         let mut uploader = UploadingTxReceiver::new(remote_client, remote_head);
         Processor::process(db_tx, from_tx, &mut uploader)?;
         if !uploader.is_done {
-            bail!(ErrorKind::TxProcessorUnfinished);
+            bail!(TolstoyError::TxProcessorUnfinished);
         }
         // Last tx uuid uploaded by the tx receiver.
         // It's going to be our new head.
@@ -222,7 +222,7 @@ impl Syncer {
         // without walking the table at all, and use the tx index.
         Processor::process(&db_tx, None, &mut inquiring_tx_receiver)?;
         if !inquiring_tx_receiver.is_done {
-            bail!(ErrorKind::TxProcessorUnfinished);
+            bail!(TolstoyError::TxProcessorUnfinished);
         }
         let have_local_changes = match inquiring_tx_receiver.last_tx {
             Some(tx) => {
@@ -257,7 +257,7 @@ impl Syncer {
                 Syncer::upload_ours(&mut db_tx, Some(upload_from_tx), &remote_client, &remote_head)?;
             } else {
                 d(&format!("Unable to fast-forward the server; missing local tx mapping"));
-                bail!(ErrorKind::TxIncorrectlyMapped(0));
+                bail!(TolstoyError::TxIncorrectlyMapped(0));
             }
             
         // We diverged from the server.
@@ -265,7 +265,7 @@ impl Syncer {
         } else {
             d(&format!("server changed since last sync."));
 
-            bail!(ErrorKind::NotYetImplemented(
+            bail!(TolstoyError::NotYetImplemented(
                 format!("Can't yet sync against changed server. Local head {:?}, remote head {:?}", locally_known_remote_head, remote_head)
             ));
         }

tolstoy/src/tx_mapper.rs

@@ -14,7 +14,7 @@ use uuid::Uuid;
 use mentat_core::Entid;
 
 use errors::{
-    ErrorKind,
+    TolstoyError,
     Result,
 };
 
@@ -59,7 +59,7 @@ impl TxMapper {
         if txs.len() == 0 {
             return Ok(None);
         } else if txs.len() > 1 {
-            bail!(ErrorKind::TxIncorrectlyMapped(txs.len()));
+            bail!(TolstoyError::TxIncorrectlyMapped(txs.len()));
         }
         Ok(Some(txs.remove(0)?))
     }
@@ -79,7 +79,7 @@ impl TxMapper {
         if uuids.len() == 0 {
             return Ok(None);
         } else if uuids.len() > 1 {
-            bail!(ErrorKind::TxIncorrectlyMapped(uuids.len()));
+            bail!(TolstoyError::TxIncorrectlyMapped(uuids.len()));
         }
         Ok(Some(uuids.remove(0)?))
     }

tools/cli/Cargo.toml

@@ -20,6 +20,8 @@ test = false
 [dependencies]
 combine = "2.2.2"
 env_logger = "0.5"
+failure = "0.1.1"
+failure_derive = "0.1.1"
 getopts = "0.2"
 lazy_static = "0.2"
 linefeed = "0.4"
@@ -28,7 +30,6 @@ tabwriter = "1"
 tempfile = "1.1"
 termion = "1"
 time = "0.1"
-error-chain = { git = "https://github.com/rnewman/error-chain", branch = "rnewman/sync" }
 
 [dependencies.rusqlite]
 version = "0.13"

tools/cli/src/mentat_cli/command_parser.rs

@@ -30,14 +30,26 @@ use combine::combinator::{
     try,
 };
 
-use errors as cli;
+use CliError;
 
 use edn;
 
+use failure::{
+    Compat,
+    Error,
+};
+
 use mentat::{
     CacheDirection,
 };
 
+#[macro_export]
+macro_rules! bail {
+    ($e:expr) => (
+        return Err($e.into());
+    )
+}
+
 pub static COMMAND_CACHE: &'static str = &"cache";
 pub static COMMAND_CLOSE: &'static str = &"close";
 pub static COMMAND_EXIT_LONG: &'static str = &"exit";
@@ -188,7 +200,7 @@ impl Command {
     }
 }
 
-pub fn command(s: &str) -> Result<Command, cli::Error> {
+pub fn command(s: &str) -> Result<Command, Error> {
     let path = || many1::<String, _>(satisfy(|c: char| !c.is_whitespace()));
     let argument = || many1::<String, _>(satisfy(|c: char| !c.is_whitespace()));
     let arguments = || sep_end_by::<Vec<_>, _, _>(many1(satisfy(|c: char| !c.is_whitespace())), many1::<Vec<_>, _>(space())).expected("arguments");
@@ -202,7 +214,7 @@ pub fn command(s: &str) -> Result<Command, cli::Error> {
     let edn_arg_parser = || spaces()
                             .with(look_ahead(string("[").or(string("{")))
                                 .with(many1::<Vec<_>, _>(try(any())))
-                                .and_then(|args| -> Result<String, cli::Error> {
+                                .and_then(|args| -> Result<String, Compat<Error>> {
                                     Ok(args.iter().collect())
                                 })
                             );
@@ -217,10 +229,10 @@ pub fn command(s: &str) -> Result<Command, cli::Error> {
             .with(arguments())
             .map(move |args| {
                 if args.len() < num_args {
-                    bail!(cli::ErrorKind::CommandParse("Missing required argument".to_string()));
+                    bail!(CliError::CommandParse("Missing required argument".to_string()));
                 }
                 if args.len() > num_args {
-                    bail!(cli::ErrorKind::CommandParse(format!("Unrecognized argument {:?}", args[num_args])));
+                    bail!(CliError::CommandParse(format!("Unrecognized argument {:?}", args[num_args])));
                 }
                 Ok(args)
             })
@@ -239,7 +251,7 @@ pub fn command(s: &str) -> Result<Command, cli::Error> {
                     .with(no_arg_parser())
                     .map(|args| {
                         if !args.is_empty() {
-                            bail!(cli::ErrorKind::CommandParse(format!("Unrecognized argument {:?}", args[0])) );
+                            bail!(CliError::CommandParse(format!("Unrecognized argument {:?}", args[0])) );
                         }
                         Ok(Command::Close)
                     });
@@ -248,7 +260,7 @@ pub fn command(s: &str) -> Result<Command, cli::Error> {
                     .with(no_arg_parser())
                     .map(|args| {
                         if !args.is_empty() {
-                            bail!(cli::ErrorKind::CommandParse(format!("Unrecognized argument {:?}", args[0])) );
+                            bail!(CliError::CommandParse(format!("Unrecognized argument {:?}", args[0])) );
                         }
                         Ok(Command::Exit)
                     });
@@ -302,7 +314,7 @@ pub fn command(s: &str) -> Result<Command, cli::Error> {
                     .with(no_arg_parser())
                     .map(|args| {
                         if !args.is_empty() {
-                            bail!(cli::ErrorKind::CommandParse(format!("Unrecognized argument {:?}", args[0])) );
+                            bail!(CliError::CommandParse(format!("Unrecognized argument {:?}", args[0])) );
                         }
                         Ok(Command::Schema)
                     });
@@ -312,10 +324,10 @@ pub fn command(s: &str) -> Result<Command, cli::Error> {
                     .with(arguments())
                     .map(|args| {
                         if args.len() < 1 {
-                            bail!(cli::ErrorKind::CommandParse("Missing required argument".to_string()));
+                            bail!(CliError::CommandParse("Missing required argument".to_string()));
                         }
                         if args.len() > 2 {
-                            bail!(cli::ErrorKind::CommandParse(format!("Unrecognized argument {:?}", args[2])));
+                            bail!(CliError::CommandParse(format!("Unrecognized argument {:?}", args[2])));
                         }
                         Ok(Command::Sync(args.clone()))
                     });
@@ -335,7 +347,7 @@ pub fn command(s: &str) -> Result<Command, cli::Error> {
 
     spaces()
     .skip(token('.'))
-    .with(choice::<[&mut Parser<Input = _, Output = Result<Command, cli::Error>>; 16], _>
+    .with(choice::<[&mut Parser<Input = _, Output = Result<Command, Error>>; 16], _>
           ([&mut try(help_parser),
             &mut try(import_parser),
             &mut try(timer_parser),
@@ -353,7 +365,7 @@ pub fn command(s: &str) -> Result<Command, cli::Error> {
             &mut try(sync_parser),
             &mut try(transact_parser)]))
         .parse(s)
-        .unwrap_or((Err(cli::ErrorKind::CommandParse(format!("Invalid command {:?}", s)).into()), "")).0
+        .unwrap_or((Err(CliError::CommandParse(format!("Invalid command {:?}", s)).into()), "")).0
 }
 
 #[cfg(test)]

tools/cli/src/mentat_cli/errors.rs

@@ -1,37 +0,0 @@
-// Copyright 2016 Mozilla
-//
-// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
-// this file except in compliance with the License. You may obtain a copy of the
-// License at http://www.apache.org/licenses/LICENSE-2.0
-// Unless required by applicable law or agreed to in writing, software distributed
-// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
-// CONDITIONS OF ANY KIND, either express or implied. See the License for the
-// specific language governing permissions and limitations under the License.
-
-#![allow(dead_code)]
-
-use rusqlite;
-
-use mentat::errors as mentat;
-
-error_chain! {
-    types {
-        Error, ErrorKind, ResultExt, Result;
-    }
-
-    foreign_links {
-        Rusqlite(rusqlite::Error);
-        IoError(::std::io::Error);
-    }
-
-    links {
-        MentatError(mentat::Error, mentat::ErrorKind);
-    }
-
-    errors {
-        CommandParse(message: String) {
-            description("An error occured parsing the entered command")
-            display("{}", message)
-        }
-    }
-}

tools/cli/src/mentat_cli/input.rs

@@ -28,7 +28,7 @@ use command_parser::{
     command,
 };
 
-use errors as cli;
+use failure::Error;
 
 /// Starting prompt
 const DEFAULT_PROMPT: &'static str = "mentat=> ";
@@ -97,7 +97,7 @@ impl InputReader {
     /// Reads a single command, item, or statement from `stdin`.
     /// Returns `More` if further input is required for a complete result.
     /// In this case, the input received so far is buffered internally.
-    pub fn read_input(&mut self) -> Result<InputResult, cli::Error> {
+    pub fn read_input(&mut self) -> Result<InputResult, Error> {
         let prompt = if self.in_process_cmd.is_some() { MORE_PROMPT } else { DEFAULT_PROMPT };
         let prompt = format!("{blue}{prompt}{reset}",
                              blue = color::Fg(::BLUE),

tools/cli/src/mentat_cli/lib.rs

@@ -10,12 +10,13 @@
 
 #![crate_name = "mentat_cli"]
 
+#[macro_use] extern crate failure_derive;
 #[macro_use] extern crate log;
 #[macro_use] extern crate lazy_static;
-#[macro_use] extern crate error_chain;
 
 extern crate combine;
 extern crate env_logger;
+extern crate failure;
 extern crate getopts;
 extern crate linefeed;
 extern crate rusqlite;
@@ -41,7 +42,12 @@ static GREEN: color::Rgb = color::Rgb(0x77, 0xFF, 0x99);
 pub mod command_parser;
 pub mod input;
 pub mod repl;
-pub mod errors;
+
+#[derive(Debug, Fail)]
+pub enum CliError {
+    #[fail(display = "{}", _0)]
+    CommandParse(String),
+}
 
 pub fn run() -> i32 {
     env_logger::init();

tools/cli/src/mentat_cli/repl.rs

@@ -11,6 +11,11 @@
 use std::io::Write;
 use std::process;
 
+use failure::{
+    err_msg,
+    Error,
+};
+
 use tabwriter::TabWriter;
 
 use termion::{
@@ -383,7 +388,7 @@ impl Repl {
         if self.path.is_empty() || path != self.path {
             let next = match encryption_key {
                 #[cfg(not(feature = "sqlcipher"))]
-                Some(_) => bail!(".open_encrypted and .empty_encrypted require the sqlcipher Mentat feature"),
+                Some(_) => return Err(err_msg(".open_encrypted and .empty_encrypted require the sqlcipher Mentat feature")),
                 #[cfg(feature = "sqlcipher")]
                 Some(k) => {
                     if empty {
@@ -467,7 +472,7 @@ impl Repl {
         output.flush().unwrap();
     }
 
-    fn print_results(&self, query_output: QueryOutput) -> Result<(), ::errors::Error> {
+    fn print_results(&self, query_output: QueryOutput) -> Result<(), Error> {
         let stdout = ::std::io::stdout();
         let mut output = TabWriter::new(stdout.lock());